diff --git a/README.md b/README.md
index 74bae044..96ad88b8 100644
--- a/README.md
+++ b/README.md
@@ -569,6 +569,14 @@ cinatra depends on asio and async_simple.
 
 press_tool depends on cinatra and cmdline.
 
+# submodule
+
+A submodule of cinatra is iguana.
+
+When you want to use this submodule, using the command `git submodule init` will pull the iguana library.
+
+If you want to use the latest iguana, please use the command `git submodule update --remote`.
+
 # 联系方式
 
 purecpp@163.com
diff --git a/lang/english/README.md b/lang/english/README.md
index 21ffe465..834dae4b 100644
--- a/lang/english/README.md
+++ b/lang/english/README.md
@@ -510,6 +510,14 @@ e.g. `-H User-Agent: coro_http_press` is to add an http header, and `-H User-Age
 
 `-r `parameter, which indicates whether to read a fixed-length response, this parameter can avoid frequent parsing of the response to optimize performance, some servers may return different lengths for the same request, in this case, do not set -r to 1, or do not set this parameter.
 
+# submodule
+
+A submodule of cinatra is iguana.
+
+When you want to use this submodule, using the command `git submodule init` will pull the iguana library.
+
+If you want to use the latest iguana, please use the command `git submodule update --remote`.
+
 ## Performance
 
 ![qps](../qps.png "qps")