diff --git a/__test__/Geometry/__snapshots__/arc.test.ts.snap b/__test__/Geometry/__snapshots__/arc.test.ts.snap
index 1d3ac6fbc..6e602d2e2 100644
--- a/__test__/Geometry/__snapshots__/arc.test.ts.snap
+++ b/__test__/Geometry/__snapshots__/arc.test.ts.snap
@@ -70,6 +70,10 @@ exports[`圆弧合并 1`] = `1`;
 
 exports[`圆弧合并 2`] = `0.5`;
 
+exports[`圆弧合并 3`] = `0.5`;
+
+exports[`圆弧合并 4`] = `0`;
+
 exports[`最近点 1`] = `
 Vector3 {
   "x": 0,
diff --git a/__test__/Geometry/arc.test.ts b/__test__/Geometry/arc.test.ts
index 36f04d79d..516248bf1 100644
--- a/__test__/Geometry/arc.test.ts
+++ b/__test__/Geometry/arc.test.ts
@@ -208,6 +208,13 @@ test('圆弧合并', () =>
     expect(arc.StartAngle).toMatchSnapshot();
     expect(arc.EndAngle).toMatchSnapshot();
 
+    //终点在里面,起点在外面
+    arc = new Arc(new Vector3(), 1, 0, 1).Reverse();
+    arc2 = new Arc(new Vector3(), 1, 5, 0.5).Reverse();
+    expect(arc.Join(arc2)).toBeTruthy();
+    expect(arc.StartAngle).toMatchSnapshot();
+    expect(arc.EndAngle).toMatchSnapshot();
+
     //包含.
     arc = new Arc(new Vector3(), 1, 0, 1).Reverse();
     arc2 = new Arc(new Vector3(), 1, 5, 3);
diff --git a/src/DatabaseServices/Arc.ts b/src/DatabaseServices/Arc.ts
index 329803f86..292948873 100644
--- a/src/DatabaseServices/Arc.ts
+++ b/src/DatabaseServices/Arc.ts
@@ -322,20 +322,25 @@ export class Arc extends Curve
                         this.ConverToCircle();//圆
                     else
                         this.StartAngle = sa;
-
                     return true;
                 }
                 else if (equaln(ea, this.m_EndAngle))//this终点对终点
                 {
                     if (saAllan > allAn)
                         this.StartAngle = sa;
-
                     return true;
                 }
-
-                if (eaAllan < saAllan && saAllan < allAn)
+                else if (this.ParamOnCurve(this.GetParamAtAngle(sa)))
+                {
+                    if (eaAllan < saAllan)
+                        this.ConverToCircle();
+                    else if (eaAllan > allAn)
+                        this.EndAngle = ea;
+                    return true;
+                }
+                else if (this.ParamOnCurve(this.GetParamAtAngle(ea)))
                 {
-                    this.ConverToCircle();//圆
+                    this.StartAngle = sa;
                     return true;
                 }
 
@@ -491,7 +496,7 @@ export class Arc extends Curve
         return this;
     }
 
-    FromThreePoint(pt1: Vector3, pt2: Vector3, pt3: Vector3)  
+    FromThreePoint(pt1: Vector3, pt2: Vector3, pt3: Vector3)
     {
         if (!(pt1 && pt2 && pt3))
             return;