diff --git a/public/javascripts/course.js b/public/javascripts/course.js
index ed920b48a..da24e2878 100644
--- a/public/javascripts/course.js
+++ b/public/javascripts/course.js
@@ -666,6 +666,7 @@ function regex_homework_end_publish_time()
         $("#homework_publish_time").val(myDate.toLocaleDateString());
     }
     var publish_time = Date.parse($("#homework_publish_time").val());
+    var end_time = Date.parse($("#homework_end_time").val());
     if(end_time < publish_time)
     {
         $("#homework_end_time_span").text("截止日期不能小于发布日期");
@@ -1258,4 +1259,4 @@ function course_outline(id){
 //    $('#course_outline_search').on('input',function(){
 //        alert('<%= @course.id%>')
 //    })
-//})
+//})