diff --git a/src/data/peakpoint.cpp b/src/data/peakpoint.cpp
index 0065d81..48f864c 100644
--- a/src/data/peakpoint.cpp
+++ b/src/data/peakpoint.cpp
@@ -188,6 +188,73 @@ QVector<QPointF> PeakPoint::getPeakPointGroup()
     return pointVtr;
 }
 
+double PeakPoint::calculateArea() {
+    //getPoint group
+    QVector<QPointF> points = getPeakPointGroup();
+#if 0
+    for(QPointF point:points){
+        qDebug()<<"x,y:"<<QString::number(point.x(),'f',3)<<","
+               <<QString::number(point.y(),'f',3);
+    }
+#endif
+    qDebug()<<QString::number(points.at(0).x(),'f',3)<<","<<
+              QString::number(points.at(points.size() - 1).x(),'f',3);
+
+    //calculate Area
+    float integral = 0.0;
+    size_t n = points.size();
+
+    if (n < 2) {
+        return integral; // 至少需要两个点才能计算积分
+    }
+
+#if 0
+    for (size_t i = 1; i < n; ++i) {
+        float dx = points[i].x() - points[i - 1].x();
+        float avg_y = (points[i].y() + points[i - 1].y()) / 2.0;
+
+#if 0
+        float step =  dx *  std::abs(avg_y);
+        qDebug()<<points[i].x()<<","<<points[i].y()<<"integral:"<<integral<<","<<step;
+#endif
+
+        integral += dx * std::abs(avg_y);
+    }
+#endif
+#if 0
+    double k = (y2 - y1) / (x2 - x1);
+    double b = y1 - k * x1;
+#endif
+    //find a line.
+    double k = (_leftSelectedPoint.y() - _rightSelectedPoint.y()) /
+            (_leftSelectedPoint.x() - _rightSelectedPoint.x());
+    double b = _leftSelectedPoint.y() - k * _leftSelectedPoint.x();
+
+    for (size_t i = 0; i < n - 1; ++i) {
+#if 1
+        double x1 = points[i].x();
+        double y1 = points[i].y();
+
+        double x2 = points[i + 1].x();
+        double y2 = points[i + 1].y();
+#endif
+        double yLine1 = k * x1 + b;
+        double yLine2  = k * x2 + b;
+
+        double diff1 = y1 - yLine1;
+        double diff2 = y2 - yLine2;
+
+        double dx = x2 - x1;
+
+        double cellArea = (diff1 + diff2) * dx /2.0;
+
+        integral += std::abs(cellArea);
+    }
+
+
+    return integral;
+}
+
 QPair<QPointF, QPointF> PeakPoint::calculateStartAndEndPoint()
 {
     QPair<QPointF,QPointF> leftMaxDiffPointPair =  PeakPoint::calculateMaxDiffPointLeft();
@@ -262,39 +329,6 @@ QPointF PeakPoint::calculateIntersection(const QPointF p1,const QPointF p2,
     }
 }
 
-float PeakPoint::calculateArea() {
-    //getPoint group
-    QVector<QPointF> points = getPeakPointGroup();
-#if 0
-    for(QPointF point:points){
-        qDebug()<<"x,y:"<<QString::number(point.x(),'f',3)<<","
-               <<QString::number(point.y(),'f',3);
-    }
-#endif
-    qDebug()<<QString::number(points.at(0).x(),'f',3)<<","<<
-              QString::number(points.at(points.size() - 1).x(),'f',3);
-
-    //calculate Area
-    float integral = 0.0;
-    size_t n = points.size();
-
-    if (n < 2) {
-        return integral; // 至少需要两个点才能计算积分
-    }
-
-    for (size_t i = 1; i < n; ++i) {
-        float dx = points[i].x() - points[i - 1].x();
-        float avg_y = (points[i].y() + points[i - 1].y()) / 2.0;
-
-        float step =  dx *  std::abs(avg_y);
-        qDebug()<<points[i].x()<<","<<points[i].y()<<"integral:"<<integral<<","<<step;
-
-        integral += dx * std::abs(avg_y);
-    }
-
-    return integral;
-}
-
 
 
 
diff --git a/src/data/peakpoint.h b/src/data/peakpoint.h
index 26e22d1..895d8c1 100644
--- a/src/data/peakpoint.h
+++ b/src/data/peakpoint.h
@@ -16,7 +16,8 @@ QString textFormat(const float enthalpyValue,
                    const float startPoint,
                    const float endPoint);
 QPair<QPointF,QPointF> calculateStartAndEndPoint();
-float calculateArea();
+double calculateArea();
+
 //private
 void updateStartEndPoint();
 QPair<QPointF,QPointF> calculateMaxDiffPointLeft();