diff --git a/PPOCRLabel/libs/canvas.py b/PPOCRLabel/libs/canvas.py
index 780ca71af55f71a79727344d5c50244b43142608..81f37995126140b03650f5ddea37ea282d5ceb09 100644
--- a/PPOCRLabel/libs/canvas.py
+++ b/PPOCRLabel/libs/canvas.py
@@ -624,6 +624,13 @@ class Canvas(QWidget):
             pal.setColor(self.backgroundRole(), QColor(232, 232, 232, 255))
             self.setPalette(pal)
 
+        # adaptive BBOX label & index font size
+        if self.pixmap:
+            h, w = self.pixmap.size().height(), self.pixmap.size().width()
+            fontszie = int(max(h, w) / 48)
+            for s in self.shapes:
+                s.fontsize = fontszie
+        
         p.end()
 
     def fillDrawing(self):
diff --git a/PPOCRLabel/libs/shape.py b/PPOCRLabel/libs/shape.py
index 1b32a6af14800de62d269461eb131d27b1038177..4e0b1f08c65ba04dd2e3fac6db29d3ab67d89f0c 100644
--- a/PPOCRLabel/libs/shape.py
+++ b/PPOCRLabel/libs/shape.py
@@ -66,6 +66,7 @@ class Shape(object):
             self.NEAR_VERTEX: (4, self.P_ROUND),
             self.MOVE_VERTEX: (1.5, self.P_SQUARE),
         }
+        self.fontsize = 8
 
         self._closed = False
 
@@ -157,7 +158,7 @@ class Shape(object):
                     min_y = min(min_y, point.y())
                 if min_x != sys.maxsize and min_y != sys.maxsize:
                     font = QFont()
-                    font.setPointSize(8)
+                    font.setPointSize(self.fontsize)
                     font.setBold(True)
                     painter.setFont(font)
                     if self.label is None:
@@ -175,7 +176,7 @@ class Shape(object):
                     min_y = min(min_y, point.y())
                 if min_x != sys.maxsize and min_y != sys.maxsize:
                     font = QFont()
-                    font.setPointSize(8)
+                    font.setPointSize(self.fontsize)
                     font.setBold(True)
                     painter.setFont(font)
                     text = ''