diff --git a/API.md b/API.md
index fb90f56..622f3e6 100644
--- a/API.md
+++ b/API.md
@@ -137,4 +137,19 @@ modal.align({left:"left", top:"top", margin: 20});
 - - - 
 
 ## close()
-`close()`
\ No newline at end of file
+`close()`
+
+- - -
+
+## onStateChanged
+
+Type: `Function`
+
+`onStateChanged` function can be defined in setConfig method or new ax5.ui.modal initialization method.
+However, you can us to define an event function after initialization, if necessary
+
+```js
+modal.onStateChanged = function(){
+    console.log(this);
+}
+```
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