diff --git a/net/cm/README.md b/net/cm/README.md
index 9f9dad8..23cf836 100644
--- a/net/cm/README.md
+++ b/net/cm/README.md
@@ -1 +1,31 @@
-This script will download *.zip and *.img files from `http://download.cyanogenmod.org/` and then upload it to baiduyun
+This script will download `*.zip` and `*.img` files from [http://download.cyanogenmod.org/](http://download.cyanogenmod.org/) and then upload it to baiduyun.
+
+## Dependency
+
+This tool requires `python3` `bypy` `python3-bs4`
+
+```
+apt-get install python3 python3-bs4
+git clone https://github.com/houtianze/bypy
+```
+
+## Usage
+
+Make sure the paths is `/root/bypy/bypy.py` `/root/cm/cm.py`, otherwise you have to modify the script for your need.
+
+**Upload**
+```
+cd ~/cm/
+screen
+./cm.py
+```
+
+This will fetch `http://download.cyanogenmod.org/` and download `*.zip` `*.img` and check their `sha1`. Then upload it to baiduyun.
+
+The default download directory is `/var/cyanogenmod`, and the default upload directory is `/YOUR_APP_DIR/cm/DEVICE`. Log file is saved in `/var/cyanogenmod/DEVICE/log/DEVICE.log`.
+
+**Generate device list**
+
+```
+./cm.py --list
+```