diff --git a/app/controllers/student_work_controller.rb b/app/controllers/student_work_controller.rb
index 79ad0d2d0..83128c45a 100644
--- a/app/controllers/student_work_controller.rb
+++ b/app/controllers/student_work_controller.rb
@@ -637,7 +637,7 @@ class StudentWorkController < ApplicationController
                 student_work.final_score = student_work.system_score
               else
                 ta_proportion = homework.homework_detail_programing.ta_proportion + homework.homework_detail_manual.ta_proportion / 2
-                final_sy_score = BigDecimal.new("#{student_work.system_score}") * BigDecimal.new("#{ta_proportion}")
+                final_sy_score = BigDecimal.new("#{student_work.system_score || 0}") * BigDecimal.new("#{ta_proportion}")
                 final_st_score = BigDecimal.new("#{student_work.student_score}") * (BigDecimal.new('1.0')  - BigDecimal.new("#{ta_proportion}"))
                 final_score = final_sy_score + final_st_score
                 student_work.final_score = format("%.2f",final_score.to_f)
@@ -647,13 +647,13 @@ class StudentWorkController < ApplicationController
                 student_work.final_score = student_work.system_score
               else
                 ta_proportion = homework.homework_detail_programing.ta_proportion + (1.0 - homework.homework_detail_manual.ta_proportion - homework.homework_detail_programing.ta_proportion) / 2
-                final_sy_score = BigDecimal.new("#{student_work.system_score}") * BigDecimal.new("#{ta_proportion}")
+                final_sy_score = BigDecimal.new("#{student_work.system_score || 0}") * BigDecimal.new("#{ta_proportion}")
                 final_ts_score = BigDecimal.new("#{student_work.teaching_asistant_score}") * (BigDecimal.new('1.0')  - BigDecimal.new("#{ta_proportion}"))
                 final_score = final_sy_score + final_ts_score
                 student_work.final_score = format("%.2f",final_score.to_f)
               end
             else
-              final_sy_score = BigDecimal.new("#{student_work.system_score}") * BigDecimal.new("#{homework.homework_detail_programing.ta_proportion}")
+              final_sy_score = BigDecimal.new("#{student_work.system_score || 0}") * BigDecimal.new("#{homework.homework_detail_programing.ta_proportion}")
               final_ts_score = BigDecimal.new("#{student_work.teaching_asistant_score}") * BigDecimal.new("#{homework.homework_detail_manual.ta_proportion}")
               final_st_score = BigDecimal.new("#{student_work.student_score}") * (BigDecimal.new('1.0')  - BigDecimal.new("#{homework.homework_detail_programing.ta_proportion}") - BigDecimal.new("#{homework.homework_detail_manual.ta_proportion}"))
               final_score = final_sy_score + final_ts_score + final_st_score
@@ -666,7 +666,7 @@ class StudentWorkController < ApplicationController
               student_work.final_score = student_work.system_score
             else
               ta_proportion = homework.homework_detail_programing.ta_proportion + homework.homework_detail_manual.ta_proportion / 2
-              final_sy_score = BigDecimal.new("#{student_work.system_score}") * BigDecimal.new("#{ta_proportion}")
+              final_sy_score = BigDecimal.new("#{student_work.system_score || 0}") * BigDecimal.new("#{ta_proportion}")
               final_st_score = BigDecimal.new("#{student_work.student_score}") * (BigDecimal.new('1.0')  - BigDecimal.new("#{ta_proportion}"))
               final_score = final_sy_score + final_st_score
               student_work.final_score = format("%.2f",final_score.to_f)
@@ -676,13 +676,13 @@ class StudentWorkController < ApplicationController
               student_work.final_score = student_work.system_score
             else
               ta_proportion = homework.homework_detail_programing.ta_proportion + (1.0 - homework.homework_detail_manual.ta_proportion - homework.homework_detail_programing.ta_proportion) / 2
-              final_sy_score = BigDecimal.new("#{student_work.system_score}") * BigDecimal.new("#{ta_proportion}")
+              final_sy_score = BigDecimal.new("#{student_work.system_score || 0}") * BigDecimal.new("#{ta_proportion}")
               final_ts_score = BigDecimal.new("#{student_work.teaching_asistant_score}") * (BigDecimal.new('1.0')  - BigDecimal.new("#{ta_proportion}"))
               final_score = final_sy_score + final_ts_score
               student_work.final_score = format("%.2f",final_score.to_f)
             end
           else
-            final_sy_score = BigDecimal.new("#{student_work.system_score}") * BigDecimal.new("#{homework.homework_detail_programing.ta_proportion}")
+            final_sy_score = BigDecimal.new("#{student_work.system_score || 0}") * BigDecimal.new("#{homework.homework_detail_programing.ta_proportion}")
             final_ts_score = BigDecimal.new("#{student_work.teaching_asistant_score}") * BigDecimal.new("#{homework.homework_detail_manual.ta_proportion}")
             final_st_score = BigDecimal.new("#{student_work.student_score}") * (BigDecimal.new('1.0')  - BigDecimal.new("#{homework.homework_detail_programing.ta_proportion}") - BigDecimal.new("#{homework.homework_detail_manual.ta_proportion}"))
             final_score = final_sy_score + final_ts_score + final_st_score
diff --git a/db/migrate/20150918004521_system_score_default.rb b/db/migrate/20150918004521_system_score_default.rb
new file mode 100644
index 000000000..6195caad9
--- /dev/null
+++ b/db/migrate/20150918004521_system_score_default.rb
@@ -0,0 +1,15 @@
+class SystemScoreDefault < ActiveRecord::Migration
+  def up
+    change_column :student_works,:system_score,:float,:default => 0
+
+
+    # StudentWork.where("system_score is null").each do |student_work|
+    #   student_work.system_score = 0
+    #   student_work.save
+    # end
+  end
+
+  def down
+    change_column :student_works,:system_score,:float
+  end
+end
diff --git a/db/migrate/20150918005722_about_normal_homework.rb b/db/migrate/20150918005722_about_normal_homework.rb
new file mode 100644
index 000000000..8e0ddf00a
--- /dev/null
+++ b/db/migrate/20150918005722_about_normal_homework.rb
@@ -0,0 +1,20 @@
+class AboutNormalHomework < ActiveRecord::Migration
+  def up
+    HomeworkCommon.where(:homework_type => 0).each do |homework|
+      unless homework.homework_detail_manual
+        homework_detail_manual = HomeworkDetailManual.new
+        homework_detail_manual.ta_proportion =  0.6
+        homework_detail_manual.comment_status = 1
+        homework_detail_manual.evaluation_start = homework.created_at
+        homework_detail_manual.evaluation_end = homework.created_at
+        homework_detail_manual.evaluation_num =  3
+        homework_detail_manual.absence_penalty = 5
+        homework_detail_manual.homework_common_id = homework.id
+        homework_detail_manual.save
+      end
+    end
+  end
+
+  def down
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 9f3cdecca..78c0802e7 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20150917022239) do
+ActiveRecord::Schema.define(:version => 20150918005722) do
 
   create_table "activities", :force => true do |t|
     t.integer  "act_id",                                  :null => false
@@ -1328,7 +1328,7 @@ ActiveRecord::Schema.define(:version => 20150917022239) do
     t.datetime "updated_at",                                                       :null => false
     t.integer  "late_penalty",                                  :default => 0
     t.integer  "absence_penalty",                               :default => 0
-    t.integer  "system_score"
+    t.float    "system_score",                                  :default => 0.0
     t.boolean  "is_test",                                       :default => false
   end