diff --git a/app/models/exercise.rb b/app/models/exercise.rb
index 0c8b97ca7..af84a5c49 100644
--- a/app/models/exercise.rb
+++ b/app/models/exercise.rb
@@ -3,9 +3,9 @@ class Exercise < ApplicationRecord
   belongs_to :exercise_bank, optional: true
   belongs_to :user
 
-  has_many :exercise_users,:dependent => :destroy
-  has_many :exercise_questions,:dependent => :destroy
-  has_many :exercise_group_settings,:dependent => :destroy
+  has_many :exercise_users
+  has_many :exercise_questions
+  has_many :exercise_group_settings
   has_many :tidings, as: :container
   has_many :course_acts, class_name: 'CourseActivity', as: :course_act, dependent: :destroy
 
@@ -19,6 +19,13 @@ class Exercise < ApplicationRecord
   validates :exercise_name, length: { maximum: 60, too_long: "60 characters is the maximum allowed" }
 
   after_create :create_exercise_list
+  after_destroy :destroy_other_relations
+
+  def destroy_other_relations
+    exercise_users.destroy_all
+    exercise_questions.destroy_all
+    exercise_group_settings.destroy_all
+  end
 
   def create_exercise_list
     str = ""
diff --git a/app/models/exercise_answer.rb b/app/models/exercise_answer.rb
index 465fa036b..96fbe17bb 100644
--- a/app/models/exercise_answer.rb
+++ b/app/models/exercise_answer.rb
@@ -3,7 +3,7 @@ class ExerciseAnswer < ApplicationRecord
   belongs_to :user
   belongs_to :exercise_question
   belongs_to :exercise_choice, optional: true
-  has_many :exercise_answer_comments, :dependent => :destroy
+  has_many :exercise_answer_comments
 
   scope :search_exercise_answer, lambda { |name,key| where("#{name} = ?",key)}
   scope :search_answer_users, lambda {|name,ids| where("#{name}":ids)}
@@ -11,4 +11,10 @@ class ExerciseAnswer < ApplicationRecord
   scope :exercise_answer_is_right, -> {where("score > ?",0.0)}  #判断答案是否正确，根据分数总和大于0
   scope :score_reviewed, lambda {where("score >= ?",0.0)}   #是否评分,用于判断主观题的
 
+  after_destroy :destroy_answers_relations
+
+  def destroy_answers_relations
+    exercise_answer_comments.destroy_all
+  end
+
 end
\ No newline at end of file
diff --git a/app/models/exercise_choice.rb b/app/models/exercise_choice.rb
index 525251ce6..f4f5c5a16 100644
--- a/app/models/exercise_choice.rb
+++ b/app/models/exercise_choice.rb
@@ -1,9 +1,16 @@
 class ExerciseChoice < ApplicationRecord
 
   belongs_to :exercise_question
-  has_many :exercise_answers, :dependent => :destroy
-  has_many :exercise_standard_answers, :dependent => :destroy
+  has_many :exercise_answers
+  has_many :exercise_standard_answers
 
   scope :find_choice_custom, lambda {|k,v| where("#{k} = ?",v)}  #根据传入的参数查找问题
   scope :left_choice_choose, lambda {|k,v| where("#{k} > ?",v)}  #根据传入的参数查找问题
+
+  after_destroy :destroy_choices_relations
+
+  def destroy_choices_relations
+    exercise_answers.destroy_all
+    exercise_standard_answers.destroy_all
+  end
 end
\ No newline at end of file
diff --git a/app/models/exercise_question.rb b/app/models/exercise_question.rb
index 607ad1a29..c236b657c 100644
--- a/app/models/exercise_question.rb
+++ b/app/models/exercise_question.rb
@@ -4,9 +4,9 @@ class ExerciseQuestion < ApplicationRecord
   belongs_to :exercise
   belongs_to :shixun,  optional: true
 
-  has_many :exercise_choices, :dependent => :destroy
+  has_many :exercise_choices
   has_many :exercise_answers
-  has_many :exercise_shixun_challenges,:dependent => :destroy
+  has_many :exercise_shixun_challenges
   has_many :exercise_shixun_answers
   has_many :exercise_answer_comments
   has_many :exercise_standard_answers
@@ -17,6 +17,12 @@ class ExerciseQuestion < ApplicationRecord
   scope :find_objective_questions, -> {where("question_type != ?",4)}  #查找全部客观题
   # scope :next_exercise, lambda {|k| where("question_number > ?",k).first}
   # scope :last_exercise, lambda {|k| where("question_number < ?",k).last}
+  after_destroy :destroy_questions_relations
+
+  def destroy_questions_relations
+    exercise_choices.destroy_all
+    exercise_shixun_challenges.destroy_all
+  end
 
   def question_type_name
     case self.question_type
diff --git a/app/models/exercise_shixun_answer.rb b/app/models/exercise_shixun_answer.rb
index 8548e497d..72a6999d6 100644
--- a/app/models/exercise_shixun_answer.rb
+++ b/app/models/exercise_shixun_answer.rb
@@ -2,7 +2,7 @@ class ExerciseShixunAnswer < ApplicationRecord
   belongs_to :exercise_question
   belongs_to :user
   belongs_to :exercise_shixun_challenge
-  has_many :exercise_answer_comments, :dependent => :destroy
+  has_many :exercise_answer_comments
   # status 0: 未通过， 1：通过
   # attr_accessible :answer_text, :score, :status
   scope :search_shixun_answers, lambda {|name,ids| where("#{name}":ids)}
@@ -10,4 +10,9 @@ class ExerciseShixunAnswer < ApplicationRecord
   scope :shixun_no_full_scores, lambda { |score| where("score > 0.0 AND score < ?",score)}
   scope :score_reviewed, lambda {where("score is not NULL AND score >= ?",0.0)}   #是否评分
 
+  after_destroy :destroy_shixun_relations
+
+  def destroy_shixun_relations
+    exercise_answer_comments.destroy_all
+  end
 end