diff --git a/keygen/README.md b/keygen/README.md
index adf3273..49e36b1 100644
--- a/keygen/README.md
+++ b/keygen/README.md
@@ -1,5 +1,26 @@
-# keygen
+# Keygen
 
 English | [简体中文](./README.zh-CN.md)
 
-Distributed Primary Key generator.
+A Distributed Primary Key generator.
+
+## Differences with the snowflake algorithm
+
+Keygen id contains a table index in it's bit sequence, so we can locate the sharding table whitout the sharding key.
+For example, use Keygen id, we could use:
+
+```
+select * from orders where id = 76362673717182593
+```
+
+Use snowflake, you should use:
+
+```
+select * from orders where id = 76362673717182593 and user_id = 100
+```
+
+The former is commonly used in CRUD codes so we made this improvement.
+
+## License
+
+This project under MIT license.
diff --git a/keygen/README.zh-CN.md b/keygen/README.zh-CN.md
index 4a3315b..92c4a36 100644
--- a/keygen/README.zh-CN.md
+++ b/keygen/README.zh-CN.md
@@ -1,5 +1,26 @@
-# keygen
+# Keygen
 
 [English](./README.md) | 简体中文
 
-分布式主键生成器。
+一个分布式主键生成器。
+
+## 与雪花算法的区别
+
+Keygen id 在其比特序列中包含了表索引，这样可以在没有分表键的情况下定位分表。
+例如，使用 Keygen id，我们可以：
+
+```
+select * from orders where id = 76362673717182593
+```
+
+使用雪花算法，则需要：
+
+```
+select * from orders where id = 76362673717182593 and user_id = 100
+```
+
+第一种情况在增删改查代码中如此常用，所以我们做了这个改进。
+
+## 许可证
+
+本项目使用 MIT 许可证。