diff --git a/public/javascripts/wechat/directives/iphone_recognize.js b/public/javascripts/wechat/directives/iphone_recognize.js
index 0d435e1a2..fabba0e51 100644
--- a/public/javascripts/wechat/directives/iphone_recognize.js
+++ b/public/javascripts/wechat/directives/iphone_recognize.js
@@ -8,9 +8,16 @@ app.directive('iphoneRecognize',function(){
         link: function(scope, element){
             var userAgent = navigator.userAgent;
             if (/ipad|iphone|mac/i.test(navigator.userAgent)){
-                element.css({"position":"relative","padding":"1px 0"});
-                $(".post-wrapper").css("margin-bottom","0");
-                $("#all_homework_reply").css("margin-bottom","0");
+                $("#postInput1").bind('focus',function(){
+                    element.css({"position":"relative","padding":"1px 0"});
+                    $(".post-wrapper").css("margin-bottom","0");
+                    $("#all_homework_reply").css("margin-bottom","0");
+                });
+                $("#postInput1").bind('blur',function(){
+                    element.css("position","fixed");
+                    $(".post-wrapper").css("margin-bottom","10px");
+                    $("#all_homework_reply").css("margin-bottom","50px");
+                });
             }
         }
     }