diff --git a/packages/draw/src/engines/uml/assembly.ts b/packages/draw/src/engines/uml/assembly.ts
index 60aceb083..0e583a9c5 100644
--- a/packages/draw/src/engines/uml/assembly.ts
+++ b/packages/draw/src/engines/uml/assembly.ts
@@ -3,6 +3,9 @@ import {
     Point,
     PointOfRectangle,
     RectangleClient,
+    SVGArcCommand,
+    distanceBetweenPointAndPoint,
+    getNearestPointBetweenPointAndArc,
     getNearestPointBetweenPointAndEllipse,
     getNearestPointBetweenPointAndSegments,
     setStrokeLinecap
@@ -12,32 +15,76 @@ import { Options } from 'roughjs/bin/core';
 import { RectangleEngine } from '../basic-shapes/rectangle';
 import { getUnitVectorByPointAndPoint, rotateVector } from '@plait/common';
 
+interface AssemblyPathData {
+    startPoint: Point;
+    line1: [Point, Point];
+    circleArcCommand: SVGArcCommand;
+    verticalArcCommand: SVGArcCommand;
+    line2: [Point, Point];
+}
+
+function generateAssemblyPath(rectangle: RectangleClient): AssemblyPathData {
+    const centerY = rectangle.y + rectangle.height / 2;
+    const firstLineEndX = rectangle.x + rectangle.width * 0.3;
+    const circleWidth = rectangle.width * 0.13;
+    const circleHeight = rectangle.height * 0.285;
+    const verticalX = firstLineEndX + circleWidth;
+    const verticalRadius = rectangle.width * 0.233;
+
+    return {
+        startPoint: [rectangle.x, centerY],
+        line1: [
+            [rectangle.x, centerY],
+            [firstLineEndX, centerY]
+        ],
+        circleArcCommand: {
+            rx: circleWidth,
+            ry: circleHeight,
+            xAxisRotation: 0,
+            largeArcFlag: 1,
+            sweepFlag: 1,
+            endX: firstLineEndX,
+            endY: centerY
+        },
+        verticalArcCommand: {
+            rx: verticalRadius,
+            ry: rectangle.height / 2,
+            xAxisRotation: 0,
+            largeArcFlag: 0,
+            sweepFlag: 1,
+            endX: verticalX,
+            endY: rectangle.y + rectangle.height
+        },
+        line2: [
+            [verticalX + verticalRadius, centerY],
+            [rectangle.x + rectangle.width, centerY]
+        ]
+    };
+}
+
 export const AssemblyEngine: ShapeEngine = {
     draw(board: PlaitBoard, rectangle: RectangleClient, options: Options) {
         const rs = PlaitBoard.getRoughSVG(board);
-        const shape = rs.path(
-            `
-        M${rectangle.x} ${rectangle.y + rectangle.height / 2} 
-        H${rectangle.x + rectangle.width * 0.3}
-        A${rectangle.width * 0.13} ${rectangle.height * 0.285}, 0, 1, 1 ${rectangle.x +
-                rectangle.width * 0.3 +
-                rectangle.width * 0.26} ${rectangle.y + rectangle.height / 2}
-        A${rectangle.width * 0.13} ${rectangle.height * 0.285}, 0, 1, 1 ${rectangle.x + rectangle.width * 0.3} ${rectangle.y +
-                rectangle.height / 2}
-        M${rectangle.x + rectangle.width * 0.3 + rectangle.width * 0.13} ${rectangle.y}
-        A${rectangle.width * 0.233} ${rectangle.height / 2}, 0, 0, 1 ${rectangle.x +
-                rectangle.width * 0.3 +
-                rectangle.width * 0.13} ${rectangle.y + rectangle.height}
-        M${rectangle.x + rectangle.width * 0.3 + rectangle.width * 0.13 + rectangle.width * 0.233} ${rectangle.y +
-                rectangle.height / 2} H${rectangle.x + rectangle.width}
-        `,
-            {
-                ...options,
-                fillStyle: 'solid'
-            }
-        );
-        setStrokeLinecap(shape, 'round');
+        const { startPoint, line1, circleArcCommand, verticalArcCommand, line2 } = generateAssemblyPath(rectangle);
+
+        const pathData = [
+            `M${startPoint[0]} ${startPoint[1]}`,
+            `H${line1[1][0]}`,
+            // 画完整的圆形：先画一个半圆，再画另一个半圆
+            `A${circleArcCommand.rx} ${circleArcCommand.ry} ${circleArcCommand.xAxisRotation} ${circleArcCommand.largeArcFlag} ${circleArcCommand.sweepFlag} ${line1[1][0] + circleArcCommand.rx * 2} ${circleArcCommand.endY}`,
+            `A${circleArcCommand.rx} ${circleArcCommand.ry} ${circleArcCommand.xAxisRotation} ${circleArcCommand.largeArcFlag} ${circleArcCommand.sweepFlag} ${circleArcCommand.endX} ${circleArcCommand.endY}`,
+            // 垂直椭圆
+            `M${verticalArcCommand.endX} ${rectangle.y}`,
+            `A${verticalArcCommand.rx} ${verticalArcCommand.ry} ${verticalArcCommand.xAxisRotation} ${verticalArcCommand.largeArcFlag} ${verticalArcCommand.sweepFlag} ${verticalArcCommand.endX} ${verticalArcCommand.endY}`,
+            // 最后一条线
+            `M${line2[0][0]} ${line2[0][1]} H${line2[1][0]}`
+        ].join(' ');
 
+        const shape = rs.path(pathData, {
+            ...options,
+            fillStyle: 'solid'
+        });
+        setStrokeLinecap(shape, 'round');
         return shape;
     },
     isInsidePoint(rectangle: RectangleClient, point: Point) {
@@ -51,16 +98,36 @@ export const AssemblyEngine: ShapeEngine = {
         return RectangleClient.getEdgeCenterPoints(rectangle);
     },
     getNearestPoint(rectangle: RectangleClient, point: Point) {
-        const nearestPoint = getNearestPointBetweenPointAndSegments(point, RectangleEngine.getCornerPoints(rectangle));
-        if (nearestPoint[0] === rectangle.x + rectangle.width / 2) {
-            return getNearestPointBetweenPointAndEllipse(
-                point,
-                [rectangle.x + rectangle.width * 0.43, rectangle.y + rectangle.height / 2],
-                rectangle.width * 0.223,
-                rectangle.height / 2
-            );
-        }
-        return nearestPoint;
+        const { line1, line2, circleArcCommand, verticalArcCommand } = generateAssemblyPath(rectangle);
+
+        // 检查直线段
+        const nearestPointForLines = getNearestPointBetweenPointAndSegments(point, [...line1, ...line2]);
+        const distanceForLines = distanceBetweenPointAndPoint(...point, ...nearestPointForLines);
+
+        // 检查中间圆形
+        const circleCenter = [line1[1][0] + circleArcCommand.rx, line1[1][1]] as Point;
+        const nearestPointForCircle = getNearestPointBetweenPointAndEllipse(
+            point,
+            circleCenter,
+            circleArcCommand.rx,
+            circleArcCommand.ry
+        );
+        const distanceForCircle = distanceBetweenPointAndPoint(...point, ...nearestPointForCircle);
+
+        // 检查垂直椭圆（使用 getNearestPointBetweenPointAndArc 处理半圆弧）
+        const arcStartPoint: Point = [verticalArcCommand.endX, rectangle.y];
+        const nearestPointForEllipse = getNearestPointBetweenPointAndArc(
+            point,
+            arcStartPoint,
+            verticalArcCommand
+        );
+        const distanceForEllipse = distanceBetweenPointAndPoint(...point, ...nearestPointForEllipse);
+
+        // 返回最近的点
+        const minDistance = Math.min(distanceForLines, distanceForCircle, distanceForEllipse);
+        if (minDistance === distanceForLines) return nearestPointForLines;
+        if (minDistance === distanceForCircle) return nearestPointForCircle;
+        return nearestPointForEllipse;
     },
     getTangentVectorByConnectionPoint(rectangle: RectangleClient, pointOfRectangle: PointOfRectangle) {
         const connectionPoint = RectangleClient.getConnectionPoint(rectangle, pointOfRectangle);