diff --git a/Cigarette/main.cpp b/Cigarette/main.cpp
index 72dd525..b7b3c76 100644
--- a/Cigarette/main.cpp
+++ b/Cigarette/main.cpp
@@ -2,6 +2,8 @@
 #include <QtWidgets/QApplication>
 #include <QPixmap>
 #include <QSplashScreen>
+#include <Windows.h>
+#include <qmessagebox.h>
 #if defined LICENSE_VERIFY
 #pragma comment(lib,"CryptoToolLib.lib")
 #include "CryptoToolLib.h"
@@ -9,6 +11,18 @@
 
 int main(int argc, char* argv[])
 {
+    QApplication a(argc, argv);
+    HANDLE hMutex = NULL;
+
+    hMutex = CreateMutex(nullptr, TRUE, L"CigratteShanghai");
+    if ((GetLastError() == ERROR_ALREADY_EXISTS) || (hMutex == NULL)) {
+        QMessageBox::warning(nullptr, "Error", "An instance of the application is already running.");
+        CloseHandle(hMutex);
+        hMutex = NULL;
+        a.closeAllWindows();
+        return 0;
+    }
+
 #if defined LICENSE_VERIFY
     if (!VerifyLicense())
     {
@@ -16,7 +30,6 @@ int main(int argc, char* argv[])
     }
 #endif
     qRegisterMetaType<cv::Mat>("cv::Mat");
-    QApplication a(argc, argv);
     QPixmap pixmap("D:/Release/splash.jpg");
     QSplashScreen splash(pixmap);
     splash.show();
@@ -25,5 +38,12 @@ int main(int argc, char* argv[])
     w.show();
     //w.showFullScreen();
     splash.finish(&w);
-    return a.exec();
+    a.exec();
+
+    if (hMutex != NULL) {
+        CloseHandle(hMutex);
+        hMutex = NULL;
+    }
+
+    return 0;
 }