diff --git a/app/helpers/members_helper.rb b/app/helpers/members_helper.rb
index 29ba94924..c8e8bd87b 100644
--- a/app/helpers/members_helper.rb
+++ b/app/helpers/members_helper.rb
@@ -44,7 +44,11 @@ module MembersHelper
   # add by nwb
   # 课程可添加的成员列表
   def render_principals_for_new_course_members(course)
-    scope = Principal.active.sorted.not_member_of_course(course).like(params[:q])
+    if params[:q] && params[:q] != ""
+      scope = Principal.active.sorted.not_member_of_course(course).like(params[:q])
+    else
+      scope = []
+    end
     principals = paginateHelper scope,10
     s = content_tag('ul', project_member_check_box_tags_ex('membership[user_ids][]', principals), :class => 'mb5', :id => 'principals')