diff --git a/app/helpers/exercises_helper.rb b/app/helpers/exercises_helper.rb
index 68f6574ee..72fbc9486 100644
--- a/app/helpers/exercises_helper.rb
+++ b/app/helpers/exercises_helper.rb
@@ -642,7 +642,7 @@ module ExercisesHelper
     end
     if student_status == 2   #当前为老师，或为学生且已提交
       user_score_pre = exercise_answers.score_reviewed
-      user_score = user_score_pre.present? ? user_score_pre.pluck(:score).sum : nil
+      user_score = user_score_pre.present? ? user_score_pre.pluck(:score).sum : "0.0"
     end
 
     if user_score.present? && (user_score > q.question_score)