diff --git a/brainpy/_src/delay.py b/brainpy/_src/delay.py
index 0c0016155..d6cdfd682 100644
--- a/brainpy/_src/delay.py
+++ b/brainpy/_src/delay.py
@@ -369,7 +369,7 @@ def update(
         else:
           self.data[0] = latest_value
 
-  def reset_state(self, batch_size: int = None):
+  def reset_state(self, batch_size: int = None, **kwargs):
     """Reset the delay data.
     """
     # initialize delay data
@@ -439,7 +439,7 @@ def __init__(
                      name=name,
                      mode=mode)
 
-  def reset_state(self, batch_size: int = None):
+  def reset_state(self, batch_size: int = None, **kwargs):
     """Reset the delay data.
     """
     self.target.value = variable_(self.target_init, self.target.size_without_batch, batch_size)
@@ -476,9 +476,9 @@ def reset_state(self, *args, **kwargs):
     pass
 
 
-def init_delay_by_return(info: Union[bm.Variable, ReturnInfo]) -> Delay:
+def init_delay_by_return(info: Union[bm.Variable, ReturnInfo], initial_delay_data=None) -> Delay:
   if isinstance(info, bm.Variable):
-    return VarDelay(info)
+    return VarDelay(info, init=initial_delay_data)
 
   elif isinstance(info, ReturnInfo):
     # batch size
@@ -510,6 +510,6 @@ def init_delay_by_return(info: Union[bm.Variable, ReturnInfo]) -> Delay:
 
     # variable
     target = bm.Variable(init, batch_axis=batch_axis, axis_names=info.axis_names)
-    return DataDelay(target, data_init=info.data)
+    return DataDelay(target, data_init=info.data, init=initial_delay_data)
   else:
     raise TypeError
diff --git a/brainpy/_src/dyn/projections/aligns.py b/brainpy/_src/dyn/projections/aligns.py
index 23b907286..c19f45844 100644
--- a/brainpy/_src/dyn/projections/aligns.py
+++ b/brainpy/_src/dyn/projections/aligns.py
@@ -27,6 +27,9 @@ def update(self, x):
     else:
       return x >> self.syn >> self.delay
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class _AlignPost(DynamicalSystem):
   def __init__(self,
@@ -39,6 +42,9 @@ def __init__(self,
   def update(self, *args, **kwargs):
     self.out.bind_cond(self.syn(*args, **kwargs))
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class _AlignPreMg(DynamicalSystem):
   def __init__(self, access, syn):
@@ -49,6 +55,9 @@ def __init__(self, access, syn):
   def update(self, *args, **kwargs):
     return self.syn(self.access())
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 def _get_return(return_info):
   if isinstance(return_info, bm.Variable):
@@ -132,6 +141,9 @@ def update(self, x):
     self.refs['out'].bind_cond(current)
     return current
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class ProjAlignPostMg1(Projection):
   r"""Synaptic projection which defines the synaptic computation with the dimension of postsynaptic neuron group.
@@ -224,6 +236,9 @@ def update(self, x):
     self.refs['syn'].add_current(current)  # synapse post current
     return current
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class ProjAlignPostMg2(Projection):
   """Synaptic projection which defines the synaptic computation with the dimension of postsynaptic neuron group.
@@ -352,6 +367,9 @@ def update(self):
     self.refs['syn'].add_current(current)  # synapse post current
     return current
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class ProjAlignPost1(Projection):
   """Synaptic projection which defines the synaptic computation with the dimension of postsynaptic neuron group.
@@ -438,6 +456,9 @@ def update(self, x):
     self.refs['syn'].add_current(current)
     return current
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class ProjAlignPost2(Projection):
   """Synaptic projection which defines the synaptic computation with the dimension of postsynaptic neuron group.
@@ -561,6 +582,9 @@ def update(self):
     self.refs['out'].bind_cond(g)  # synapse post current
     return g
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class ProjAlignPreMg1(Projection):
   """Synaptic projection which defines the synaptic computation with the dimension of presynaptic neuron group.
@@ -686,6 +710,9 @@ def update(self, x=None):
     self.refs['out'].bind_cond(current)
     return current
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class ProjAlignPreMg2(Projection):
   """Synaptic projection which defines the synaptic computation with the dimension of presynaptic neuron group.
@@ -814,6 +841,9 @@ def update(self):
     self.refs['out'].bind_cond(current)
     return current
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class ProjAlignPre1(Projection):
   """Synaptic projection which defines the synaptic computation with the dimension of presynaptic neuron group.
@@ -933,6 +963,9 @@ def update(self, x=None):
     self.refs['out'].bind_cond(current)
     return current
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
 
 class ProjAlignPre2(Projection):
   """Synaptic projection which defines the synaptic computation with the dimension of presynaptic neuron group.
@@ -1052,4 +1085,7 @@ def update(self):
     spk = self.refs['delay'].at(self.name)
     g = self.comm(self.syn(spk))
     self.refs['out'].bind_cond(g)
-    return g
\ No newline at end of file
+    return g
+
+  def reset_state(self, *args, **kwargs):
+    pass
diff --git a/brainpy/_src/dyn/projections/others.py b/brainpy/_src/dyn/projections/others.py
index 44cdfb043..72a77298f 100644
--- a/brainpy/_src/dyn/projections/others.py
+++ b/brainpy/_src/dyn/projections/others.py
@@ -54,6 +54,9 @@ def __init__(
     self.freq = check.is_float(freq, min_bound=0., allow_int=True)
     self.weight = check.is_float(weight, allow_int=True)
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
   def update(self):
     p = self.freq * share['dt'] / 1e3
     a = self.num_input * p
diff --git a/brainpy/_src/dyn/projections/plasticity.py b/brainpy/_src/dyn/projections/plasticity.py
index 01f3e7bea..7c176c125 100644
--- a/brainpy/_src/dyn/projections/plasticity.py
+++ b/brainpy/_src/dyn/projections/plasticity.py
@@ -174,6 +174,9 @@ def __init__(
     self.A1 = parameter(A1, sizes=self.pre_num)
     self.A2 = parameter(A2, sizes=self.post_num)
 
+  def reset_state(self, *args, **kwargs):
+    pass
+
   def _init_trace(
       self,
       target: DynamicalSystem,
diff --git a/brainpy/_src/dyn/synapses/delay_couplings.py b/brainpy/_src/dyn/synapses/delay_couplings.py
index a4ecaa67c..ef43139da 100644
--- a/brainpy/_src/dyn/synapses/delay_couplings.py
+++ b/brainpy/_src/dyn/synapses/delay_couplings.py
@@ -191,7 +191,7 @@ def __init__(
   def update(self):
     # delays
     axis = self.coupling_var1.ndim
-    delay_var: bm.LengthDelay = self.get_delay_var(f'delay_{id(self.delay_var)}')[0]
+    delay_var = self.get_delay_var(f'delay_{id(self.delay_var)}')
     if self.delay_steps is None:
       diffusive = (jnp.expand_dims(self.coupling_var1.value, axis=axis) -
                    jnp.expand_dims(self.coupling_var2.value, axis=axis - 1))
@@ -201,13 +201,13 @@ def update(self):
         indices = (slice(None, None, None), jnp.arange(self.coupling_var1.size),)
       else:
         indices = (jnp.arange(self.coupling_var1.size),)
-      f = vmap(lambda steps: delay_var(steps, *indices), in_axes=1)  # (..., pre.num)
+      f = vmap(lambda steps: delay_var.retrieve(steps, *indices), in_axes=1)  # (..., pre.num)
       delays = f(self.delay_steps)  # (..., post.num, pre.num)
       diffusive = (jnp.moveaxis(bm.as_jax(delays), axis - 1, axis) -
                    jnp.expand_dims(self.coupling_var2.value, axis=axis - 1))  # (..., pre.num, post.num)
       diffusive = (self.conn_mat * diffusive).sum(axis=axis - 1)
     elif self.delay_type == 'int':
-      delayed_data = delay_var(self.delay_steps)  # (..., pre.num)
+      delayed_data = delay_var.retrieve(self.delay_steps)  # (..., pre.num)
       diffusive = (jnp.expand_dims(delayed_data, axis=axis) -
                    jnp.expand_dims(self.coupling_var2.value, axis=axis - 1))  # (..., pre.num, post.num)
       diffusive = (self.conn_mat * diffusive).sum(axis=axis - 1)
@@ -276,7 +276,7 @@ def __init__(
   def update(self):
     # delay function
     axis = self.coupling_var.ndim
-    delay_var: bm.LengthDelay = self.get_delay_var(f'delay_{id(self.delay_var)}')[0]
+    delay_var = self.get_delay_var(f'delay_{id(self.delay_var)}')
     if self.delay_steps is None:
       additive = self.coupling_var @ self.conn_mat
     elif self.delay_type == 'array':
@@ -284,11 +284,11 @@ def update(self):
         indices = (slice(None, None, None), jnp.arange(self.coupling_var.size),)
       else:
         indices = (jnp.arange(self.coupling_var.size),)
-      f = vmap(lambda steps: delay_var(steps, *indices), in_axes=1)  # (.., pre.num,)
+      f = vmap(lambda steps: delay_var.retrieve(steps, *indices), in_axes=1)  # (.., pre.num,)
       delays = f(self.delay_steps)  # (..., post.num, pre.num)
       additive = (self.conn_mat * jnp.moveaxis(delays, axis - 1, axis)).sum(axis=axis - 1)
     elif self.delay_type == 'int':
-      delayed_var = delay_var(self.delay_steps)  # (..., pre.num)
+      delayed_var = delay_var.retrieve(self.delay_steps)  # (..., pre.num)
       additive = delayed_var @ self.conn_mat
     else:
       raise ValueError
diff --git a/brainpy/_src/dynold/synapses/abstract_models.py b/brainpy/_src/dynold/synapses/abstract_models.py
index 60af8ee89..aef74a756 100644
--- a/brainpy/_src/dynold/synapses/abstract_models.py
+++ b/brainpy/_src/dynold/synapses/abstract_models.py
@@ -124,7 +124,7 @@ def reset_state(self, batch_size=None):
   def update(self, pre_spike=None):
     # pre-synaptic spikes
     if pre_spike is None:
-      pre_spike = self.get_delay_data(f"{self.pre.name}.spike", delay_step=self.delay_step)
+      pre_spike = self.get_delay_data(f"{self.pre.name}.spike", self.delay_step)
     pre_spike = bm.as_jax(pre_spike)
     if self.stop_spike_gradient:
       pre_spike = jax.lax.stop_gradient(pre_spike)
diff --git a/brainpy/_src/dynsys.py b/brainpy/_src/dynsys.py
index e79f0a2df..d85c16d9c 100644
--- a/brainpy/_src/dynsys.py
+++ b/brainpy/_src/dynsys.py
@@ -1,9 +1,9 @@
 # -*- coding: utf-8 -*-
 
 import collections
-import gc
 import inspect
 import warnings
+import numbers
 from typing import Union, Dict, Callable, Sequence, Optional, Any
 
 import numpy as np
@@ -12,7 +12,7 @@
 from brainpy._src.context import share
 from brainpy._src.deprecations import _update_deprecate_msg
 from brainpy._src.initialize import parameter, variable_
-from brainpy._src.mixin import SupportAutoDelay, Container, SupportInputProj, DelayRegister, global_delay_data
+from brainpy._src.mixin import SupportAutoDelay, Container, SupportInputProj, DelayRegister, _get_delay_tool
 from brainpy.errors import NoImplementationError, UnsupportedError, APIChangedError
 from brainpy.types import ArrayType, Shape
 
@@ -27,6 +27,8 @@
   'Dynamic', 'Projection',
 ]
 
+
+IonChaDyn = None
 SLICE_VARS = 'slice_vars'
 
 
@@ -87,14 +89,10 @@ def __init__(
                                f'which are parents of {self.supported_modes}, '
                                f'but we got {self.mode}.')
 
-    # Attribute for "ReceiveInputProj"
+    # Attribute for "SupportInputProj"
+    # each instance of "SupportInputProj" should have a "cur_inputs" attribute
     self.cur_inputs = bm.node_dict()
 
-    # local delay variables:
-    # Compatible for ``DelayRegister``
-    # TODO: will be deprecated in the future
-    self.local_delay_vars: Dict = bm.node_dict()
-
     # the before- / after-updates used for computing
     # added after the version of 2.4.3
     self.before_updates: Dict[str, Callable] = bm.node_dict()
@@ -135,18 +133,6 @@ def has_aft_update(self, key: Any):
     """Whether this node has the after update of the given ``key``."""
     return key in self.after_updates
 
-  def reset_bef_updates(self, *args, **kwargs):
-    """Reset all before updates."""
-    for node in self.before_updates.values():
-      if isinstance(node, DynamicalSystem):
-        node.reset(*args, **kwargs)
-
-  def reset_aft_updates(self, *args, **kwargs):
-    """Reset all after updates."""
-    for node in self.after_updates.values():
-      if isinstance(node, DynamicalSystem):
-        node.reset(*args, **kwargs)
-
   def update(self, *args, **kwargs):
     """The function to specify the updating rule.
     """
@@ -163,7 +149,10 @@ def reset(self, *args, include_self: bool = False, **kwargs):
       include_self: bool. Reset states including the node self. Please turn on this if the node has
         implemented its ".reset_state()" function.
     """
-    child_nodes = self.nodes(include_self=include_self).subset(DynamicalSystem).unique()
+    global IonChaDyn
+    if IonChaDyn is None:
+      from brainpy._src.dyn.base import IonChaDyn
+    child_nodes = self.nodes(include_self=include_self).subset(DynamicalSystem).not_subset(IonChaDyn).unique()
     for node in child_nodes.values():
       node.reset_state(*args, **kwargs)
 
@@ -236,6 +225,44 @@ def mode(self, value):
                        f'but we got {type(value)}: {value}')
     self._mode = value
 
+  def register_local_delay(
+      self,
+      var_name: str,
+      delay_name: str,
+      delay: Union[numbers.Number, ArrayType] = None,
+  ):
+    """Register local relay at the given delay time.
+
+    Args:
+      var_name: str. The name of the delay target variable.
+      delay_name: str. The name of the current delay data.
+      delay: The delay time.
+    """
+    delay_identifier, init_delay_by_return = _get_delay_tool()
+    delay_identifier = delay_identifier + var_name
+    try:
+      target = getattr(self, var_name)
+    except AttributeError:
+      raise AttributeError(f'This node {self} does not has attribute of "{var_name}".')
+    if not self.has_aft_update(delay_identifier):
+      self.add_aft_update(delay_identifier, init_delay_by_return(target))
+    delay_cls = self.get_aft_update(delay_identifier)
+    delay_cls.register_entry(delay_name, delay)
+
+  def get_local_delay(self, var_name, delay_name):
+    """Get the delay at the given identifier (`name`).
+
+    Args:
+      var_name: The name of the target delay variable.
+      delay_name: The identifier of the delay.
+
+    Returns:
+      The delayed data at the given delay position.
+    """
+    delay_identifier, init_delay_by_return = _get_delay_tool()
+    delay_identifier = delay_identifier + var_name
+    return self.get_aft_update(delay_identifier).at(delay_name)
+
   def _compatible_update(self, *args, **kwargs):
     update_fun = super().__getattribute__('update')
     update_args = tuple(inspect.signature(update_fun).parameters.values())
@@ -320,11 +347,8 @@ def _compatible_update(self, *args, **kwargs):
           return ret
       return update_fun(*args, **kwargs)
 
-  # def __getattr__(self, item):
-  #   if item == 'update':
-  #     return self._compatible_update  # update function compatible with previous ``update()`` function
-  #   else:
-  #     return object.__getattribute__(self, item)
+  def _get_update_fun(self):
+    return object.__getattribute__(self, 'update')
 
   def __getattribute__(self, item):
     if item == 'update':
@@ -332,9 +356,6 @@ def __getattribute__(self, item):
     else:
       return super().__getattribute__(item)
 
-  def _get_update_fun(self):
-    return object.__getattribute__(self, 'update')
-
   def __repr__(self):
     return f'{self.name}(mode={self.mode})'
 
@@ -353,29 +374,6 @@ def __call__(self, *args, **kwargs):
       model(ret)
     return ret
 
-  def __del__(self):
-    """Function for handling `del` behavior.
-
-    This function is used to pop out the variables which registered in global delay data.
-    """
-    try:
-      if hasattr(self, 'local_delay_vars'):
-        for key in tuple(self.local_delay_vars.keys()):
-          val = global_delay_data.pop(key)
-          del val
-          val = self.local_delay_vars.pop(key)
-          del val
-      if hasattr(self, 'implicit_nodes'):
-        for key in tuple(self.implicit_nodes.keys()):
-          del self.implicit_nodes[key]
-      if hasattr(self, 'implicit_vars'):
-        for key in tuple(self.implicit_vars.keys()):
-          del self.implicit_vars[key]
-      for key in tuple(self.__dict__.keys()):
-        del self.__dict__[key]
-    finally:
-      gc.collect()
-
   def __rrshift__(self, other):
     """Support using right shift operator to call modules.
 
@@ -434,10 +432,6 @@ def update(self, *args, **kwargs):
     for node in nodes.not_subset(Dynamic).not_subset(Projection).values():
       node()
 
-    # update delays
-    # TODO: Will be deprecated in the future
-    self.update_local_delays(nodes)
-
 
 class Network(DynSysGroup):
   """A group of :py:class:`~.DynamicalSystem`s which defines the nodes and edges in a network.
diff --git a/brainpy/_src/mixin.py b/brainpy/_src/mixin.py
index 37d3ca3b7..39c3ace6b 100644
--- a/brainpy/_src/mixin.py
+++ b/brainpy/_src/mixin.py
@@ -1,16 +1,16 @@
+# -*- coding: utf-8 -*-
+
 import numbers
 import sys
+import warnings
 from dataclasses import dataclass
 from typing import Union, Dict, Callable, Sequence, Optional, TypeVar, Any
 from typing import (_SpecialForm, _type_check, _remove_dups_flatten)
 
 import jax
-import jax.numpy as jnp
-import numpy as np
 
 from brainpy import math as bm, tools
 from brainpy._src.math.object_transform.naming import get_unique_name
-from brainpy._src.initialize import parameter
 from brainpy.types import ArrayType
 
 if sys.version_info.minor > 8:
@@ -26,6 +26,7 @@
   'MixIn',
   'ParamDesc',
   'ParamDescInit',
+  'DelayRegister',
   'AlignPost',
   'Container',
   'TreeNode',
@@ -38,7 +39,19 @@
   'SupportOffline',
 ]
 
-global_delay_data = dict()
+
+def _get_delay_tool():
+  global delay_identifier, init_delay_by_return
+  if init_delay_by_return is None: from brainpy._src.delay import init_delay_by_return
+  if delay_identifier is None: from brainpy._src.delay import delay_identifier
+  return delay_identifier, init_delay_by_return
+
+
+def _get_dynsys():
+  global DynamicalSystem
+  if DynamicalSystem is None: from brainpy._src.dynsys import DynamicalSystem
+  return DynamicalSystem
+
 
 
 class MixIn(object):
@@ -272,41 +285,6 @@ def check_hierarchy(self, root, leaf):
 
 
 class DelayRegister(MixIn):
-  local_delay_vars: bm.node_dict
-
-  def register_delay_at(
-      self,
-      name: str,
-      delay: Union[numbers.Number, ArrayType] = None,
-  ):
-    """Register relay at the given delay time.
-
-    Args:
-      name: str. The identifier of the delay.
-      delay: The delay time.
-    """
-    global delay_identifier, init_delay_by_return, DynamicalSystem
-    if init_delay_by_return is None: from brainpy._src.delay import init_delay_by_return
-    if delay_identifier is None: from brainpy._src.delay import delay_identifier
-    if DynamicalSystem is None: from brainpy._src.dynsys import DynamicalSystem
-
-    assert isinstance(self, SupportAutoDelay), f'self must be an instance of {SupportAutoDelay.__name__}'
-    assert isinstance(self, DynamicalSystem), f'self must be an instance of {DynamicalSystem.__name__}'
-    if not self.has_aft_update(delay_identifier):
-      self.add_aft_update(delay_identifier, init_delay_by_return(self.return_info()))
-    delay_cls = self.get_aft_update(delay_identifier)
-    delay_cls.register_entry(name, delay)
-
-  def get_delay_at(self, name):
-    """Get the delay at the given identifier (`name`).
-
-    Args:
-      name: The identifier of the delay.
-
-    Returns:
-      The delay data.
-    """
-    return self.get_aft_update(delay_identifier).at(name)
 
   def register_delay(
       self,
@@ -324,71 +302,23 @@ def register_delay(
       initial_delay_data: The initializer for the delay data.
 
     Returns:
-      delay_step: The number of the delay steps.
+      delay_pos: The position of the delay.
     """
-    # warnings.warn('\n'
-    #               'Starting from brainpy>=2.4.4, instead of ".register_delay()", '
-    #               'we recommend the user to first use ".register_delay_at()", '
-    #               'then use ".get_delay_at()" to access the delayed data. '
-    #               '".register_delay()" will be removed after 2.5.0.',
-    #               UserWarning)
-
-    # delay steps
-    if delay_step is None:
-      delay_type = 'none'
-    elif isinstance(delay_step, (int, np.integer, jnp.integer)):
-      delay_type = 'homo'
-    elif isinstance(delay_step, (bm.ndarray, jnp.ndarray, np.ndarray)):
-      if delay_step.size == 1 and delay_step.ndim == 0:
-        delay_type = 'homo'
-      else:
-        delay_type = 'heter'
-        delay_step = bm.asarray(delay_step)
-    elif callable(delay_step):
-      delay_step = parameter(delay_step, delay_target.shape, allow_none=False)
-      delay_type = 'heter'
-    else:
-      raise ValueError(f'Unknown "delay_steps" type {type(delay_step)}, only support '
-                       f'integer, array of integers, callable function, brainpy.init.Initializer.')
-    if delay_type == 'heter':
-      if delay_step.dtype not in [bm.int32, bm.int64]:
-        raise ValueError('Only support delay steps of int32, int64. If your '
-                         'provide delay time length, please divide the "dt" '
-                         'then provide us the number of delay steps.')
-      if delay_target.shape[0] != delay_step.shape[0]:
-        raise ValueError(f'Shape is mismatched: {delay_target.shape[0]} != {delay_step.shape[0]}')
-    if delay_type != 'none':
-      max_delay_step = int(bm.max(delay_step))
-
-    # delay target
-    if delay_type != 'none':
-      if not isinstance(delay_target, bm.Variable):
-        raise ValueError(f'"delay_target" must be an instance of Variable, but we got {type(delay_target)}')
-
-    # delay variable
-    # TODO
-    if delay_type != 'none':
-      if identifier not in global_delay_data:
-        delay = bm.LengthDelay(delay_target, max_delay_step, initial_delay_data)
-        global_delay_data[identifier] = (delay, delay_target)
-        self.local_delay_vars[identifier] = delay
-      else:
-        delay = global_delay_data[identifier][0]
-        if delay is None:
-          delay = bm.LengthDelay(delay_target, max_delay_step, initial_delay_data)
-          global_delay_data[identifier] = (delay, delay_target)
-          self.local_delay_vars[identifier] = delay
-        elif delay.num_delay_step - 1 < max_delay_step:
-          global_delay_data[identifier][0].reset(delay_target, max_delay_step, initial_delay_data)
-    else:
-      if identifier not in global_delay_data:
-        global_delay_data[identifier] = (None, delay_target)
-    return delay_step
+    _delay_identifier, _init_delay_by_return = _get_delay_tool()
+    DynamicalSystem = _get_dynsys()
+    assert isinstance(self, DynamicalSystem), f'self must be an instance of {DynamicalSystem.__name__}'
+    _delay_identifier = _delay_identifier + identifier
+    if not self.has_aft_update(_delay_identifier):
+      self.add_aft_update(_delay_identifier, _init_delay_by_return(delay_target, initial_delay_data))
+    delay_cls = self.get_aft_update(_delay_identifier)
+    name = get_unique_name('delay')
+    delay_cls.register_entry(name, delay_step)
+    return name
 
   def get_delay_data(
       self,
       identifier: str,
-      delay_step: Optional[Union[int, bm.Array, jax.Array]],
+      delay_pos: str,
       *indices: Union[int, slice, bm.Array, jax.Array],
   ):
     """Get delay data according to the provided delay steps.
@@ -397,7 +327,7 @@ def get_delay_data(
     ----------
     identifier: str
       The delay variable name.
-    delay_step: Optional, int, ArrayType
+    delay_pos: str
       The delay length.
     indices: optional, int, slice, ArrayType
       The indices of the delay.
@@ -407,34 +337,10 @@ def get_delay_data(
     delay_data: ArrayType
       The delay data at the given time.
     """
-    # warnings.warn('\n'
-    #               'Starting from brainpy>=2.4.4, instead of ".get_delay_data()", '
-    #               'we recommend the user to first use ".register_delay_at()", '
-    #               'then use ".get_delay_at()" to access the delayed data.'
-    #               '".get_delay_data()" will be removed after 2.5.0.',
-    #               UserWarning)
-
-    if delay_step is None:
-      return global_delay_data[identifier][1].value
-
-    if identifier in global_delay_data:
-      if bm.ndim(delay_step) == 0:
-        return global_delay_data[identifier][0](delay_step, *indices)
-      else:
-        if len(indices) == 0:
-          indices = (bm.arange(delay_step.size),)
-        return global_delay_data[identifier][0](delay_step, *indices)
-
-    elif identifier in self.local_delay_vars:
-      if bm.ndim(delay_step) == 0:
-        return self.local_delay_vars[identifier](delay_step)
-      else:
-        if len(indices) == 0:
-          indices = (bm.arange(delay_step.size),)
-        return self.local_delay_vars[identifier](delay_step, *indices)
-
-    else:
-      raise ValueError(f'{identifier} is not defined in delay variables.')
+    _delay_identifier, _init_delay_by_return = _get_delay_tool()
+    _delay_identifier = _delay_identifier + identifier
+    delay_cls = self.get_aft_update(_delay_identifier)
+    return delay_cls.at(delay_pos, *indices)
 
   def update_local_delays(self, nodes: Union[Sequence, Dict] = None):
     """Update local delay variables.
@@ -448,22 +354,8 @@ def update_local_delays(self, nodes: Union[Sequence, Dict] = None):
     nodes: sequence, dict
       The nodes to update their delay variables.
     """
-    global DynamicalSystem
-    if DynamicalSystem is None:
-      from brainpy._src.dynsys import DynamicalSystem
-
-    # update delays
-    if nodes is None:
-      nodes = tuple(self.nodes(level=1, include_self=False).subset(DynamicalSystem).unique().values())
-    elif isinstance(nodes, dict):
-      nodes = tuple(nodes.values())
-    if not isinstance(nodes, (tuple, list)):
-      nodes = (nodes,)
-    for node in nodes:
-      for name in node.local_delay_vars:
-        delay = global_delay_data[name][0]
-        target = global_delay_data[name][1]
-        delay.update(target.value)
+    warnings.warn('.update_local_delays() has been removed since brainpy>=2.4.6',
+                  DeprecationWarning)
 
   def reset_local_delays(self, nodes: Union[Sequence, Dict] = None):
     """Reset local delay variables.
@@ -473,23 +365,14 @@ def reset_local_delays(self, nodes: Union[Sequence, Dict] = None):
     nodes: sequence, dict
       The nodes to Reset their delay variables.
     """
-    global DynamicalSystem
-    if DynamicalSystem is None:
-      from brainpy._src.dynsys import DynamicalSystem
-
-    # reset delays
-    if nodes is None:
-      nodes = self.nodes(level=1, include_self=False).subset(DynamicalSystem).unique().values()
-    elif isinstance(nodes, dict):
-      nodes = nodes.values()
-    for node in nodes:
-      for name in node.local_delay_vars:
-        delay = global_delay_data[name][0]
-        target = global_delay_data[name][1]
-        delay.reset(target.value)
+    warnings.warn('.reset_local_delays() has been removed since brainpy>=2.4.6',
+                  DeprecationWarning)
 
   def get_delay_var(self, name):
-    return global_delay_data[name]
+    _delay_identifier, _init_delay_by_return = _get_delay_tool()
+    _delay_identifier = _delay_identifier + name
+    delay_cls = self.get_aft_update(_delay_identifier)
+    return delay_cls
 
 
 class SupportInputProj(MixIn):
@@ -599,10 +482,12 @@ def unbind_cond(self):
 class SupportSTDP(MixIn):
   """Support synaptic plasticity by modifying the weights.
   """
-  def update_STDP(self,
-                  dW: Union[bm.Array, jax.Array],
-                  constraints: Optional[Callable] = None,
-                  ):
+
+  def update_STDP(
+      self,
+      dW: Union[bm.Array, jax.Array],
+      constraints: Optional[Callable] = None,
+  ):
     raise NotImplementedError
 
 
diff --git a/brainpy/_src/tests/test_mixin.py b/brainpy/_src/tests/test_mixin.py
index 8a1aece7c..5fbab7b9f 100644
--- a/brainpy/_src/tests/test_mixin.py
+++ b/brainpy/_src/tests/test_mixin.py
@@ -42,9 +42,12 @@ class TestDelayRegister(unittest.TestCase):
   def test2(self):
     bp.share.save(i=0)
     lif = bp.dyn.Lif(10)
-    lif.register_delay_at('a', 10.)
-    data = lif.get_delay_at('a')
+    lif.register_local_delay('spike', 'a', 10.)
+    data = lif.get_local_delay('spike', 'a')
     self.assertTrue(bm.allclose(data, bm.zeros(10)))
 
+    with self.assertRaises(AttributeError):
+      lif.register_local_delay('a', 'a', 10.)
+
 
 
diff --git a/brainpy/mixin.py b/brainpy/mixin.py
index ab3c3cd37..232fd744e 100644
--- a/brainpy/mixin.py
+++ b/brainpy/mixin.py
@@ -1,14 +1,14 @@
 
 from brainpy._src.mixin import (
   MixIn as MixIn,
-  SupportInputProj as SupportInputProj,
   AlignPost as AlignPost,
-  SupportAutoDelay as SupportAutoDelay,
   ParamDesc as ParamDesc,
   ParamDescInit as ParamDescInit,
   BindCondData as BindCondData,
   Container as Container,
   TreeNode as TreeNode,
   JointType as JointType,
-  SupportSTDP as SupportPlasticity,
+  SupportAutoDelay as SupportAutoDelay,
+  SupportInputProj as SupportInputProj,
+  SupportSTDP as SupportSTDP,
 )
diff --git a/tests/simulation/test_net_rate_FHN.py b/tests/simulation/test_net_rate_FHN.py
index 157eeb78a..de90794d7 100644
--- a/tests/simulation/test_net_rate_FHN.py
+++ b/tests/simulation/test_net_rate_FHN.py
@@ -9,6 +9,7 @@
 show = False
 bm.set_platform('cpu')
 
+
 class Network(bp.Network):
   def __init__(self, signal_speed=20.):
     super(Network, self).__init__()