diff --git a/backend/include/bs-utility.h b/backend/include/bs-utility.h
index 32c7ee0..f093bd4 100644
--- a/backend/include/bs-utility.h
+++ b/backend/include/bs-utility.h
@@ -125,6 +125,7 @@ class BookItemClass {
   char ISBN[21], name[61], author[61], keyword[61];
   double price;
   int quantity_remain;
+  int bid;
 };
 
 class FinanceItemClass {
diff --git a/backend/include/database.h b/backend/include/database.h
index 3a836ac..fd6f43b 100644
--- a/backend/include/database.h
+++ b/backend/include/database.h
@@ -28,7 +28,7 @@ class BookDataBase {
  public:
   void Open(std::string file_name);
   bool HaveISBN(const std::string &ISBN);
-  bool HaveISBN(const std::string &ISBN,BookItemClass &ret);
+  bool HaveISBN(const std::string &ISBN, BookItemClass &ret);
   void CreateEmptyBook(const std::string &ISBN);
   void QueryBook(const std::string &ISBN, const std::string &name,
                  const std::string &author, const std::string &keyword,
@@ -41,10 +41,16 @@ class BookDataBase {
 class LogDataBase {
   DriveArray<FinanceItemClass> finance_data;
   DriveArray<OperationLogItemClass> operation_log_data;
+  int finance_operation_count;
 
  public:
+  ~LogDataBase() { finance_data.write_info(finance_operation_count, 1); }
   void Open(std::string file_name);
+  void AddSell(int book_id, int quantity, double total_price);
+  void AddImport(int book_id, int quantity, double total_price);
+  std::pair<double, double> QueryFinance(int count = -1);
   void QueryFinance(int count, std::vector<FinanceItemClass> &ret);
+  int TotalFinanceOperationCount() noexcept { return finance_operation_count; }
 };
 
 #endif  // PROTECTOR_DATABASE_HPP
\ No newline at end of file
diff --git a/backend/src/database.cpp b/backend/src/database.cpp
index b42ddb0..764c002 100644
--- a/backend/src/database.cpp
+++ b/backend/src/database.cpp
@@ -17,6 +17,7 @@ void BookDataBase::Open(std::string file_name) {
 
 void LogDataBase::Open(std::string file_name) {
   finance_data.OpenFile(file_name + ".finance");
+  finance_data.get_info(finance_operation_count, 1);
   operation_log_data.OpenFile(file_name + ".log");
 }
 
@@ -94,6 +95,8 @@ void BookDataBase::CreateEmptyBook(const std::string &ISBN) {
   tmp.author[0] = 0;
   tmp.keyword[0] = 0;
   int idx = full_book_data.write(tmp);
+  tmp.bid = idx;
+  full_book_data.update(tmp, idx);
   ISBN2index.Insert(ISBN, idx);
   name2index.Insert("", idx);
   author2index.Insert("", idx);
@@ -234,4 +237,36 @@ void BookDataBase::QueryBook(const std::string &ISBN, const std::string &name,
        [](const BookItemClass &a, const BookItemClass &b) {
          return strcmp(a.ISBN, b.ISBN) < 0;
        });
+}
+
+void LogDataBase::AddImport(int book_id, int quantity, double total_price) {
+  FinanceItemClass tmp;
+  tmp.book_id = book_id;
+  tmp.quantity = quantity;
+  tmp.total_price = -total_price;
+  finance_data.write(tmp);
+  finance_operation_count++;
+}
+
+void LogDataBase::AddSell(int book_id, int quantity, double total_price) {
+  FinanceItemClass tmp;
+  tmp.book_id = book_id;
+  tmp.quantity = quantity;
+  tmp.total_price = total_price;
+  finance_data.write(tmp);
+  finance_operation_count++;
+}
+
+std::pair<double, double> LogDataBase::QueryFinance(int count) {
+  double total_sell = 0, total_import = 0;
+  if (count == -1) count = finance_operation_count;
+  for (int i = 1; i <= count; i++) {
+    FinanceItemClass tmp;
+    finance_data.read(tmp, finance_operation_count + 1 - i);
+    if (tmp.total_price > 0)
+      total_sell += tmp.total_price;
+    else
+      total_import -= tmp.total_price;
+  }
+  return std::make_pair(total_sell, total_import);
 }
\ No newline at end of file
diff --git a/backend/src/engine.cpp b/backend/src/engine.cpp
index 6f22a9e..5a5cacf 100644
--- a/backend/src/engine.cpp
+++ b/backend/src/engine.cpp
@@ -269,6 +269,7 @@ std::vector<std::string> BookStoreEngineClass::ExecuteBuy(
     return std::vector<std::string>({"Invalid"});
   book_data_base.ModifyInfo(ISBN, "", "", "", "", -1,
                             tmp.quantity_remain - quantity);
+  log_data_base.AddSell(tmp.bid, quantity, tmp.price * quantity);
   /*浮点数输出购买图书所需的总金额，小数点后有且仅有两位小数*/
   std::vector<std::string> ans;
   unsigned long long cost_tmp = tmp.price * quantity * 100 + 0.5;
@@ -355,13 +356,32 @@ std::vector<std::string> BookStoreEngineClass::ExecuteImport(
   book_data_base.HaveISBN(login_stack.top().second, tmp);
   book_data_base.ModifyInfo(login_stack.top().second, "", "", "", "", -1,
                             tmp.quantity_remain + quantity);
+  log_data_base.AddImport(tmp.bid, quantity, total_cost);
   return std::vector<std::string>();
 }
 
 std::vector<std::string> BookStoreEngineClass::ExecuteShowFinance(
     const std::string &cmd,
     std::stack<std::pair<std::string, std::string>> &login_stack) {
-  return std::vector<std::string>();
+  int count;
+  if (!CommandShowfinanceLexer(cmd, count))
+    return std::vector<std::string>({"Invalid"});
+  if (login_stack.empty() ||
+      user_data_base.GetPrevilege(login_stack.top().first) < 7)
+    return std::vector<std::string>({"Invalid"});
+  if (count > log_data_base.TotalFinanceOperationCount())
+    return std::vector<std::string>({"Invalid"});
+  if (count == 0) return std::vector<std::string>({""});
+  std::pair<double, double> ret = log_data_base.QueryFinance(count);
+  std::string ans;
+  unsigned long long income_tmp = ret.first * 100 + 0.5;
+  unsigned long long outcome_tmp = ret.second * 100 + 0.5;
+  ans =
+      "+ " + std::to_string(income_tmp / 100) + '.' +
+      std::to_string(income_tmp % 100 / 10) + std::to_string(income_tmp % 10) +
+      " - " + std::to_string(outcome_tmp / 100) + '.' +
+      std::to_string(outcome_tmp % 100 / 10) + std::to_string(outcome_tmp % 10);
+  return std::vector<std::string>({ans});
 }
 
 std::vector<std::string> BookStoreEngineClass::ExecuteLog(
diff --git a/backend/src/lexer.cpp b/backend/src/lexer.cpp
index 658f5a3..a73d2d2 100644
--- a/backend/src/lexer.cpp
+++ b/backend/src/lexer.cpp
@@ -424,6 +424,7 @@ bool CommandShowfinanceLexer(const std::string &command, int &count) {
     std::stringstream ss(command);
     std::string token;
     ss >> token;
+    ss >> token;
     long long count_tmp = -1;
     ss >> count_tmp;
     if (count_tmp > 2147483647) return false;