diff --git a/app/controllers/courses_controller.rb b/app/controllers/courses_controller.rb
index ef9204f04..4ddf5186d 100644
--- a/app/controllers/courses_controller.rb
+++ b/app/controllers/courses_controller.rb
@@ -26,21 +26,31 @@ class CoursesController < ApplicationController
   def join
     if User.current.logged?
       course = Course.find(params[:object_id])
-      if params[:course_password] == course.password
-        members = []
-        members << Member.new(:role_ids => [10], :user_id => User.current.id)
-        course.members << members
-
-        StudentsForCourse.create(:student_id => User.current.id, :course_id => params[:object_id])
-        @state = 0
+      unless User.current.member_of_course? course
+        if params[:course_password] == course.password
+          members = []
+          members << Member.new(:role_ids => [10], :user_id => User.current.id)
+          course.members << members
+
+          StudentsForCourse.create(:student_id => User.current.id, :course_id => params[:object_id])
+          @state = 0
+        else
+          @state = 1
+        end
       else
-        @state = 1
+        @state = 3
       end
     end
     respond_to do |format|
       # format.html { redirect_to_referer_or {render :text => (watching ? 'Watcher added.' : 'Watcher removed.'), :layout => true}}
       format.js { render :partial => 'set_join', :locals => {:user => User.current, :course => Course.find(params[:object_id]), :object_id => params[:object_id]} }
     end
+  rescue Exception => e
+    @state = 4
+    respond_to do |format|
+      # format.html { redirect_to_referer_or {render :text => (watching ? 'Watcher added.' : 'Watcher removed.'), :layout => true}}
+      format.js { render :partial => 'set_join', :locals => {:user => User.current, :course => nil, :object_id => nil} }
+    end
   end
 
   def unjoin
@@ -61,9 +71,7 @@ class CoursesController < ApplicationController
   end
 
   def join_private_courses
-
     respond_to do |format|
-      # format.html { redirect_to_referer_or {render :text => (watching ? 'Watcher added.' : 'Watcher removed.'), :layout => true}}
       format.js
     end
   end
diff --git a/app/views/courses/_join_private_course.html.erb b/app/views/courses/_join_private_course.html.erb
index 592c79ba1..60223922f 100644
--- a/app/views/courses/_join_private_course.html.erb
+++ b/app/views/courses/_join_private_course.html.erb
@@ -36,7 +36,7 @@
     }
 </style>
 
-<h3 class="title">请输入相关信息</h3>
+<h3 class="title">加入公开课程或私有课程</h3>
 
 <%= form_tag({:controller => 'courses',
               :action => 'join'},
@@ -46,6 +46,7 @@
     <div>
       <span>课程ID：</span>
       <%= text_field_tag 'object_id', nil, :style=>'width:80%'%>
+      <span style="padding-left: 55px;color: red;">(课程ID是课程的网址中出现的序号)</span>
     </div>
     <div>
       <span>密码&nbsp;&nbsp;&nbsp;：</span>
diff --git a/app/views/courses/_set_join.js.erb b/app/views/courses/_set_join.js.erb
index a4b5dd3c6..8b5c1fb36 100644
--- a/app/views/courses/_set_join.js.erb
+++ b/app/views/courses/_set_join.js.erb
@@ -1,4 +1,6 @@
-$("#<%=object_id%>").replaceWith('<%= escape_javascript join_in_course_for_list(course, user) %>');
+<% if object_id%>
+    $("#<%=object_id%>").replaceWith('<%= escape_javascript join_in_course_for_list(course, user) %>');
+<% end %>
 <% if @state %>
 	<% if @state == 0 %>
 		alert("加入成功")
@@ -6,7 +8,11 @@ $("#<%=object_id%>").replaceWith('<%= escape_javascript join_in_course_for_list(
 		alert("密码错误")
 	<% elsif @state == 2 %>
 		alert("课程已过期\n请联系课程管理员重启课程。(在配置课程处)")
-	<% else %>
+	<% elsif @state == 3 %>
+        alert("您已经加入了课程");
+    <% elsif @state == 3 %>
+        alert("您已经的课程不存在")
+    <% else %>
 		alert("未知错误，请稍后再试")
 	<% end %>
 <% end %>
diff --git a/app/views/welcome/_more_course.html.erb b/app/views/welcome/_more_course.html.erb
index d48050a63..a5464c27c 100644
--- a/app/views/welcome/_more_course.html.erb
+++ b/app/views/welcome/_more_course.html.erb
@@ -5,6 +5,6 @@
     <% end %>
     &nbsp;&nbsp;&nbsp;&nbsp;
 <% end %>
-<%= link_to "加入课程", join_private_courses_courses_path ,:remote => true, :class => 'icon icon-add' %>
+<%= link_to l(:label_course_join_student), join_private_courses_courses_path ,:remote => true, :class => 'icon icon-add' %>
 &nbsp;&nbsp;&nbsp;&nbsp;
 <%= link_to l(:label_more), {:controller => 'courses', :action => 'index', :school_id => school_id} %>
\ No newline at end of file