diff --git a/example/images/isat.yaml b/example/images/isat.yaml
index fc38e77..9b725dd 100644
--- a/example/images/isat.yaml
+++ b/example/images/isat.yaml
@@ -1,3 +1,4 @@
+contour_mode: external
 label:
 - color: '#000000'
   name: __background__
@@ -19,3 +20,6 @@ label:
   name: cake
 - color: '#5c3566'
   name: fence
+language: en
+mask_alpha: 0.4
+vertex_size: 2
diff --git a/widgets/canvas.py b/widgets/canvas.py
index 490bd31..b6e12ad 100644
--- a/widgets/canvas.py
+++ b/widgets/canvas.py
@@ -307,8 +307,16 @@ class AnnotationScene(QtWidgets.QGraphicsScene):
                 deleted_layer = item.zValue()
                 del item
             elif isinstance(item, Vertex):
-                index = item.polygon.vertexs.index(item)
+                polygon = item.polygon
+                index = polygon.vertexs.index(item)
                 item.polygon.removePoint(index)
+                # 如果剩余顶点少于三个，删除多边形
+                if len(polygon.vertexs) < 3:
+                    self.mainwindow.polygons.remove(polygon)
+                    polygon.delete()
+                    self.removeItem(polygon)
+                    deleted_layer = polygon.zValue()
+                    del polygon
 
         if deleted_layer is not None:
             for p in self.mainwindow.polygons: