diff --git a/app/controllers/exercises_controller.rb b/app/controllers/exercises_controller.rb
index 79bed2d25..d8278faff 100644
--- a/app/controllers/exercises_controller.rb
+++ b/app/controllers/exercises_controller.rb
@@ -1297,7 +1297,7 @@ class ExercisesController < ApplicationController
               if @user_course_identity > Course::ASSISTANT_PROFESSOR
                 tip_exception(403,"无权限操作")
               else
-                if @export_ex_users.exercise_user_committed.size == 0
+                if (@exercise_users_size == 0) ||( @export_ex_users&.exercise_user_committed.size == 0)
                   normal_status(-1,"暂无用户提交")
                 else
                   get_export_users(@exercise,@course,@export_ex_users)