diff --git a/logPlus/formdraw.cpp b/logPlus/formdraw.cpp
index 6aa4808..cff5e8d 100644
--- a/logPlus/formdraw.cpp
+++ b/logPlus/formdraw.cpp
@@ -912,6 +912,7 @@ void FormDraw::initWave(QMyCustomPlot *widget, QString strSlfName, QString strWa
     logio->CloseWave(index);
     delete logio;
 
+    bool bFistValue=false;
     float vmax = -9999;//(float)_nSamples;
     float vmin = -9999;
     //
@@ -931,6 +932,12 @@ void FormDraw::initWave(QMyCustomPlot *widget, QString strSlfName, QString strWa
             {
                 continue;
             }
+            if(bFistValue==false)
+            {
+                //最大值，最小值默认采用第一个有效值
+                bFistValue=true;
+                vmax = vmin = val;
+            }
             //
             if(vmax<val)vmax=val;
             if(vmin>val)vmin=val;