diff --git a/ui/views/system_tools/screen_capture.py b/ui/views/system_tools/screen_capture.py
index 8d8ca07..ea567b9 100644
--- a/ui/views/system_tools/screen_capture.py
+++ b/ui/views/system_tools/screen_capture.py
@@ -74,13 +74,44 @@ class ScreenCaptureOverlay(QtWidgets.QWidget):
         self.activateWindow()
         self.raise_()
 
+    @staticmethod
+    def _scale_rect(rect, logical_size, native_size):
+        """把 Qt 逻辑坐标选区映射到抓屏位图的原生像素坐标。"""
+        if (logical_size.width() <= 0 or logical_size.height() <= 0
+                or native_size.width() <= 0 or native_size.height() <= 0):
+            return QtCore.QRect()
+
+        logical_bounds = QtCore.QRect(QtCore.QPoint(), logical_size)
+        clipped = rect.normalized().intersected(logical_bounds)
+        if clipped.isEmpty():
+            return QtCore.QRect()
+
+        scale_x = native_size.width() / logical_size.width()
+        scale_y = native_size.height() / logical_size.height()
+        left = round(clipped.x() * scale_x)
+        top = round(clipped.y() * scale_y)
+        right = round((clipped.x() + clipped.width()) * scale_x)
+        bottom = round((clipped.y() + clipped.height()) * scale_y)
+
+        left = max(0, min(native_size.width(), left))
+        top = max(0, min(native_size.height(), top))
+        right = max(left, min(native_size.width(), right))
+        bottom = max(top, min(native_size.height(), bottom))
+        return QtCore.QRect(left, top, right - left, bottom - top)
+
+    def _native_rect(self, rect):
+        """返回选区在当前抓屏位图中的原生像素矩形。"""
+        if self._full_pixmap is None or self._full_pixmap.isNull():
+            return QtCore.QRect()
+        return self._scale_rect(rect, self.size(), self._full_pixmap.size())
+
     def paintEvent(self, event):
         if not self._full_pixmap:
             return
         painter = QtGui.QPainter(self)
 
         # 1. 绘制屏幕截图作为背景
-        painter.drawPixmap(0, 0, self._full_pixmap)
+        painter.drawPixmap(self.rect(), self._full_pixmap, self._full_pixmap.rect())
         # 2. 半透明遮罩
         painter.fillRect(self.rect(), QtGui.QColor(0, 0, 0, 100))
 
@@ -92,15 +123,17 @@ class ScreenCaptureOverlay(QtWidgets.QWidget):
                 rect = self._current_rect
 
             if rect.width() > 0 and rect.height() > 0:
+                native_rect = self._native_rect(rect)
                 # 3. 选区内重绘原图（去掉遮罩，形成高亮效果）
-                painter.drawPixmap(rect, self._full_pixmap, rect)
+                painter.drawPixmap(rect, self._full_pixmap, native_rect)
                 # 4. 蓝色边框
                 pen = QtGui.QPen(QtGui.QColor(0, 120, 215), 2)
                 painter.setPen(pen)
                 painter.setBrush(QtCore.Qt.BrushStyle.NoBrush)
                 painter.drawRect(rect)
                 # 5. 尺寸标注
-                size_text = f"{rect.width()} x {rect.height()}"
+                # 标签显示最终文件的真实像素，而不是受系统缩放影响的逻辑尺寸。
+                size_text = f"{native_rect.width()} x {native_rect.height()} px"
                 font = painter.font()
                 font.setPointSize(9)
                 painter.setFont(font)
@@ -177,15 +210,12 @@ class ScreenCaptureOverlay(QtWidgets.QWidget):
     def _on_confirm(self):
         """确认截图：裁剪并发射信号"""
         if self._full_pixmap and self._current_rect.width() > 5 and self._current_rect.height() > 5:
-            dpr = self._full_pixmap.devicePixelRatio()
-            phys_rect = QtCore.QRect(
-                int(self._current_rect.x() * dpr),
-                int(self._current_rect.y() * dpr),
-                int(self._current_rect.width() * dpr),
-                int(self._current_rect.height() * dpr),
-            )
-            captured = self._full_pixmap.toImage().copy(phys_rect)
-            self.screenshot_captured.emit(captured)
+            native_rect = self._native_rect(self._current_rect)
+            if not native_rect.isEmpty():
+                captured = self._full_pixmap.toImage().copy(native_rect)
+                # 截图是普通位图；避免下游再次按桌面 DPR 缩小显示。
+                captured.setDevicePixelRatio(1.0)
+                self.screenshot_captured.emit(captured)
         self.close()
 
     def _on_cancel(self):