diff --git a/app/forms/examination_banks/save_exam_form.rb b/app/forms/examination_banks/save_exam_form.rb
index 1835baa82..b84b32eb1 100644
--- a/app/forms/examination_banks/save_exam_form.rb
+++ b/app/forms/examination_banks/save_exam_form.rb
@@ -7,6 +7,9 @@ class ExaminationBanks::SaveExamForm
   validates :sub_discipline_id, presence: true
   validates :difficulty, presence: true, inclusion: {in: 1..3}, numericality: { only_integer: true }
   validates :name, presence: true, length: { maximum: 60 }
-  validates :duration, numericality: { only_integer: true, greater_than: 0 }
+  validate :validate_duration
 
+  def validate_duration
+    raise '时长应为大于0的整数' if duration.present? && duration.to_i < 1
+  end
 end
\ No newline at end of file
diff --git a/app/services/examination_banks/save_examination_bank_service.rb b/app/services/examination_banks/save_examination_bank_service.rb
index ab13e2412..1db165785 100644
--- a/app/services/examination_banks/save_examination_bank_service.rb
+++ b/app/services/examination_banks/save_examination_bank_service.rb
@@ -11,7 +11,7 @@ class ExaminationBanks::SaveExaminationBankService < ApplicationService
 
     exam.name = params[:name].to_s.strip
     exam.difficulty = params[:difficulty]
-    exam.duration = params[:duration]
+    exam.duration = params[:duration].present? ? params[:duration].to_i : nil
     exam.sub_discipline_id = params[:sub_discipline_id]
     exam.save!