diff --git a/app/controllers/members_controller.rb b/app/controllers/members_controller.rb
index d0be72961..ba312c74a 100644
--- a/app/controllers/members_controller.rb
+++ b/app/controllers/members_controller.rb
@@ -99,7 +99,7 @@ class MembersController < ApplicationController
           @project.members << members
           # added by nie
           @project.project_infos << project_info
-          @project.user_grades << user_grades
+          @project.user_grades << user_grades unless user_grades.first.user_id.nil?
           # end
         end
         if members.present? && members.all? { |m| m.valid? }
@@ -108,7 +108,11 @@ class MembersController < ApplicationController
           end
         end
         if params[:flag]
-          flash[:notice] = l(:label_invite_success)
+          unless members.present? && members.all? {|m| m.valid? }
+            flash[:error] = members.collect {|m| m.errors.full_messages}.flatten.uniq.join(', ')
+          else
+            flash[:notice] = l(:label_invite_success)
+          end
           respond_to do |format|
             format.html { redirect_to invite_members_project_url(@project) }
           end