diff --git a/app/controllers/messages_controller.rb b/app/controllers/messages_controller.rb
index 5bdc3e053..90da7d8e5 100644
--- a/app/controllers/messages_controller.rb
+++ b/app/controllers/messages_controller.rb
@@ -102,7 +102,9 @@ class MessagesController < ApplicationController
     return normal_status(403, "您没有权限进行该操作") if current_user != @message.author && !current_user.teacher_of_course?(@message.board.course)
 
     begin
-      @message.update_attributes(message_params)
+      h = {is_md: true}
+      m_params = message_params.merge(h)
+      @message.update_attributes(m_params)
       Attachment.associate_container(params[:attachment_ids], @message.id, @message.class.name)
       @message.update_content(params[:content])
     rescue Exception => e