diff --git a/app/helpers/courses_helper.rb b/app/helpers/courses_helper.rb
index b4b89bb0f..b03f6cfa1 100644
--- a/app/helpers/courses_helper.rb
+++ b/app/helpers/courses_helper.rb
@@ -104,10 +104,17 @@ module CoursesHelper
     garble count
   end
 
-  alias studentCountOrigin studentCount
+  # 注意：此方法有问题，速度慢且结果不准
+ # alias studentCountOrigin studentCount
+  #def studentCount course
+   # count = studentCountOrigin course
+    #garble count
+ # end
+
+  # 学生人数计算
+  # add by nwb
   def studentCount course
-    count = studentCountOrigin course
-    garble count
+    course.student.count
   end
 
   def eventToLanguageCourse event_type, course
diff --git a/app/models/course.rb b/app/models/course.rb
index 1c20edb72..75bac905c 100644
--- a/app/models/course.rb
+++ b/app/models/course.rb
@@ -21,7 +21,7 @@ class Course < ActiveRecord::Base
   has_many :homeworks, :through => :homework_for_courses, :source => :bid, :dependent => :destroy
   has_many :journals_for_messages, :as => :jour, :dependent => :destroy
   has_many :homework_for_courses, :dependent => :destroy
-  has_many :student, :through => :students_for_courses, :source => :user
+  has_many :student, :class_name => 'StudentsForCourse', :source => :user
   has_many :course_infos, :class_name => 'CourseInfos',:dependent => :destroy
   has_many :enabled_modules, :dependent => :delete_all
   has_many :boards, :dependent => :destroy, :order => "position ASC"