diff --git a/src/Add-on/DrawLine.ts b/src/Add-on/DrawLine.ts
index 8428033e8..2cb5163c4 100644
--- a/src/Add-on/DrawLine.ts
+++ b/src/Add-on/DrawLine.ts
@@ -3,6 +3,7 @@ import hotkeys from 'hotkeys-js-ext';
 import { Vector3 } from 'three';
 import { app } from '../ApplicationServices/Application';
 import { CircleInternalTangentLines, CircleOuterTangentLines } from '../Common/CurveUtils';
+import { Arc } from '../DatabaseServices/Entity/Arc';
 import { Circle } from '../DatabaseServices/Entity/Circle';
 import { Line } from '../DatabaseServices/Entity/Line';
 import { Command } from '../Editor/CommandMachine';
@@ -83,7 +84,7 @@ export class DrawLine implements Command
         UCSUtils.SetUCSFromPointRes(ptRes);
 
         let ptLast = ptRes.Point;
-        let firstSnapModeIsTan = ptRes.SnapMode === ObjectSnapMode.Tan && ptRes.SnapEntity;
+        let firstSnapModeIsTan = ptRes.SnapMode === ObjectSnapMode.Tan && (ptRes.SnapEntity instanceof Circle || ptRes.SnapEntity instanceof Arc);
         let firstTangeCircle = ptRes.SnapEntity as Circle;
 
         const TempUndo = () =>
@@ -143,7 +144,7 @@ export class DrawLine implements Command
             if (ptRes.Status === PromptStatus.OK)
             {
                 //第一个是切点 第二个也是选切点
-                if (ptRes.SnapMode === ObjectSnapMode.Tan && firstSnapModeIsTan && firstTangeCircle && pts.length === 1 && ptRes.SnapEntity)
+                if (ptRes.SnapMode === ObjectSnapMode.Tan && firstSnapModeIsTan && pts.length === 1 && (ptRes.SnapEntity instanceof Circle || ptRes.SnapEntity instanceof Arc))
                 {
                     let secondTangeCircle = ptRes.SnapEntity as Circle;
                     //计算最优切线