diff --git a/app/services/private_messages/create_service.rb b/app/services/private_messages/create_service.rb
index 88f3a084f..89365c4a7 100644
--- a/app/services/private_messages/create_service.rb
+++ b/app/services/private_messages/create_service.rb
@@ -30,6 +30,6 @@ class PrivateMessages::CreateService < ApplicationService
 
   def validate!
     raise Error, '内容不能为空' if content.blank?
-    raise Error, '内容太长' if content.size > 255
+    raise Error, '内容太长' if content.size > 500
   end
 end
\ No newline at end of file