diff --git a/lib/tasks/excellent_course_exercise.rake b/lib/tasks/excellent_course_exercise.rake
index e05a813f4..c3700957c 100644
--- a/lib/tasks/excellent_course_exercise.rake
+++ b/lib/tasks/excellent_course_exercise.rake
@@ -36,14 +36,15 @@ namespace :excellent_course_exercise do
     # index < pass_count 之前的学生都是通关的，之后的未通过
     members.each_with_index do |member, index|
       exercise_user = exercise.exercise_users.where(user_id: member.user_id).take
-      if exercise_question_ids.length == 20
+      question_length = exercise_question_ids.length
+      if question_length == 20
         rand_num = index < pass_count - 1 ? rand(15..20) : rand(1..10)
-      elsif exercise_question_ids.length == 17
+      elsif question_length == 17
         rand_num = index < pass_count - 1 ? rand(12..17) : rand(1..9)
-      elsif exercise_question_ids.length == 39
+      elsif question_length == 39
         rand_num = index < pass_count - 1 ? rand(30..39) : rand(1..18)
       else
-        rand_num = exercise_question_ids.length
+        rand_num = index < pass_count - 1 ? rand((question_length-3)..question_length) : rand(1..(question_length-8))
       end
 
       if exercise_user && exercise_user.commit_status == 0