diff --git a/kea/app_hm.py b/kea/app_hm.py
index 6b716f8..7b5fbc8 100644
--- a/kea/app_hm.py
+++ b/kea/app_hm.py
@@ -51,7 +51,7 @@ def _package_init(self, package_name):
     @property
     def _dumpsys_package_info(self):
         from .adapter.hdc import HDC_EXEC
-        cmd = [HDC_EXEC, "shell", "bm", "dump", "-n", self.package_name]
+        cmd = [HDC_EXEC, "-t", self.settings.device_serial, "shell", "bm", "dump", "-n", self.package_name]
         r = subprocess.check_output(cmd, text=True)
         package_info_str = r.split("\n", maxsplit=1)[-1]
         import json
diff --git a/kea/core.py b/kea/core.py
index 3956a66..f5b549a 100644
--- a/kea/core.py
+++ b/kea/core.py
@@ -18,7 +18,7 @@
 @dataclass
 class Setting:
     apk_path: str
-    device_serial: str ="emulator-5554"
+    device_serial: str = None
     output_dir:str ="output"
     is_emulator: bool =True     #True for emulator, false for real device.
     policy_name: str =input_manager.DEFAULT_POLICY
diff --git a/kea/start.py b/kea/start.py
index 4186937..79cc30a 100644
--- a/kea/start.py
+++ b/kea/start.py
@@ -1,6 +1,6 @@
-from .input_manager import DEFAULT_DEVICE_SERIAL, DEFAULT_POLICY, DEFAULT_TIMEOUT
+from .input_manager import DEFAULT_POLICY, DEFAULT_TIMEOUT
 from .core import Kea, Setting, start_kea
-from .utils import get_yml_config
+from .utils import get_yml_config, checkconfig, automatic_set_device_serial
 
 import importlib
 import os
@@ -13,7 +13,7 @@ def parse_args():
     parser = argparse.ArgumentParser(description="Start kea to test app.",
                                      formatter_class=argparse.RawTextHelpFormatter)
     parser.add_argument("-f",nargs="+", action="store",dest="files", help="The python files to be tested.")
-    parser.add_argument("-d", "--device_serial", action="store", dest="device_serial", default=DEFAULT_DEVICE_SERIAL,
+    parser.add_argument("-d", "--device_serial", action="store", dest="device_serial", default=None,
                         help="The serial number of target device (use `adb devices` to find)")
     parser.add_argument("-a","--apk", action="store", dest="apk_path",
                         help="The file path to target APK")
@@ -112,43 +112,14 @@ def get_mobile_driver(settings:"Setting"):
         from kea.pdl_hm import PDL
         return PDL(serial=settings.device_serial)
 
-def checkconfig(options):
-    if not options.apk_path:
-        raise AttributeError("No target app. Use -a to specify the app")
-    if not str(options.apk_path).endswith((".apk", ".hap")):
-        COLOR_YELLOW = "\033[93m"
-        COLOR_RESET = "\033[0m"
-        print(f"{COLOR_YELLOW}Warning: {options.apk_path} is not a package file, trying to start with a package name{COLOR_RESET}")
-        check_package_existance(options)
-        options.is_package = True
-    else:
-        options.is_package = False
-    if not options.files:
-        raise AttributeError("No property. Use -f to specify the proeprty")
-    if not options.output_dir:
-        raise AttributeError("No output directory. Use -o to specify the output directory.")
 
-def check_package_existance(options):
-    if not options.is_harmonyos:
-        cmd = ["adb", "-s", options.serial, "shell", "pm", "list", "package"] if options.serial else ["adb", "shell", "pm", "list", "package"] 
-        dump_packages = subprocess.check_output(cmd, text=True)
-        package_list = [_.split(":")[-1] for _ in dump_packages.split()]
-        if not options.package_name in package_list:
-            raise AttributeError(f"No pacakge named {options.package_name} installed on device.")    
-    else:
-        from .adapter.hdc import HDC_EXEC
-        cmd = [HDC_EXEC, "-t", options.device_serial, "shell", "bm", "dump", "-a"] if options.device_serial else [HDC_EXEC, "shell", "bm", "dump", "-a"] 
-        dump_packages = subprocess.check_output(cmd, text=True)
-        package_list = dump_packages.split()
-        if not (package_name := options.apk_path) in package_list:
-            raise AttributeError(f"No pacakge named {package_name} installed on device.")  
-        
     
 
 def main():
     options = parse_args()
     if options.load_config:
         options = parse_ymal_args(options)
+    automatic_set_device_serial(options=options)
     checkconfig(options)
     settings =  Setting(apk_path=options.apk_path,
                        device_serial=options.device_serial,
diff --git a/kea/utils.py b/kea/utils.py
index d76914d..db3dd1d 100644
--- a/kea/utils.py
+++ b/kea/utils.py
@@ -7,6 +7,11 @@
 import warnings
 import pkg_resources
 import yaml
+
+from typing import TYPE_CHECKING
+if TYPE_CHECKING:
+    from .core import Setting
+
 # logcat regex, which will match the log message generated by `adb logcat -v threadtime`
 LOGCAT_THREADTIME_RE = re.compile(
     '^(?P<date>\S+)\s+(?P<time>\S+)\s+(?P<pid>[0-9]+)\s+(?P<tid>[0-9]+)\s+'
@@ -255,4 +260,64 @@ def __call__(cls, *args, **kwargs):
         if cls not in cls._instances:
             instance = super().__call__(*args, **kwargs)
             cls._instances[cls] = instance
-        return cls._instances[cls]
\ No newline at end of file
+        return cls._instances[cls]
+
+def check_package_existance(options):
+    import subprocess
+    if not options.is_harmonyos:
+        cmd = ["adb", "-s", options.device_serial, "shell", "pm", "list", "package"] 
+        dump_packages = subprocess.check_output(cmd, text=True)
+        package_list = [_.split(":")[-1] for _ in dump_packages.split()]
+        if not options.package_name in package_list:
+            raise AttributeError(f"No pacakge named {options.package_name} installed on device.")    
+    else:
+        from .adapter.hdc import HDC_EXEC
+        cmd = [HDC_EXEC, "-t", options.device_serial, "shell", "bm", "dump", "-a"]
+        dump_packages = subprocess.check_output(cmd, text=True)
+        package_list = dump_packages.split()
+        if not (package_name := options.apk_path) in package_list:
+            raise AttributeError(f"No pacakge named {package_name} installed on device.")  
+
+def checkconfig(options):
+    if not options.apk_path:
+        raise AttributeError("No target app. Use -a to specify the app")
+    if not str(options.apk_path).endswith((".apk", ".hap")):
+        COLOR_YELLOW = "\033[93m"
+        COLOR_RESET = "\033[0m"
+        print(f"{COLOR_YELLOW}Warning: {options.apk_path} is not a package file, trying to start with a package name{COLOR_RESET}")
+        check_package_existance(options)
+        options.is_package = True
+    else:
+        options.is_package = False
+    if not options.files:
+        raise AttributeError("No property. Use -f to specify the proeprty")
+    if not options.output_dir:
+        raise AttributeError("No output directory. Use -o to specify the output directory.")
+
+def automatic_set_device_serial(options):
+    if options.device_serial is not None:
+        return    
+    
+    import subprocess
+    if not options.is_harmonyos:
+        cmd = ["adb", "devices"]
+        r = subprocess.check_output(cmd, text=True)
+        device_list = []
+        for line in r.splitlines():
+            if line and line.strip() != "List of devices attached":
+                device_list.append(line.split()[0])
+        if len(device_list) == 0:
+            raise AttributeError("No connected device")
+        if len(device_list) > 1:
+            raise AttributeError("Too many attached device, please target it with a device serial")
+        options.device_serial = device_list[0].strip()
+    else:
+        from .adapter.hdc import HDC_EXEC
+        cmd = [HDC_EXEC, "list", "targets"]
+        r = subprocess.check_output(cmd, text=True)
+        device_list = [_.strip() for _ in r.splitlines()]
+        if len(device_list) == 0:
+            raise AttributeError("No connected device")
+        if len(device_list) > 1:
+            raise AttributeError("Too many attached device, please target it with a device serial")
+        options.device_serial = device_list[0].strip()
\ No newline at end of file