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 9d2a7eddc..694361203 100644
--- a/__test__/Geometry/arc.test.ts
+++ b/__test__/Geometry/arc.test.ts
@@ -212,6 +212,13 @@ 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);
@@ -288,3 +295,5 @@ test('容差相接', () =>
 
     expect(arc.AllAngle).toBe(Math.PI * 2);
 });
+
+//file.only
diff --git a/src/DatabaseServices/Arc.ts b/src/DatabaseServices/Arc.ts
index 498c3ff4a..4347e8fba 100644
--- a/src/DatabaseServices/Arc.ts
+++ b/src/DatabaseServices/Arc.ts
@@ -300,26 +300,47 @@ export class Arc extends Curve
                 let saAllan = this.ComputeAnlge(sa);
                 let eaAllan = this.ComputeAnlge(ea);
 
-                if (this.ParamOnCurve(this.GetParamAtAngle(ea)))//this终点对终点
+                if (equaln(sa, this.m_StartAngle)) //this起点对起点
                 {
-                    if (eaAllan < saAllan || equaln(sa, this.m_StartAngle))
+                    if (eaAllan > allAn)
+                        this.EndAngle = ea;
+
+                    return true;
+                }
+                else if (equaln(sa, this.m_EndAngle))//this终点对起点
+                {
+                    if (eaAllan < allAn || equaln(ea, this.m_StartAngle))
                         this.ConverToCircle();//圆
-                    else if (saAllan > allAn)
-                        this.StartAngle = sa;
+                    else
+                        this.EndAngle = ea;
+
                     return true;
                 }
-                else if (this.ParamOnCurve(this.GetParamAtAngle(sa))) //this起点对起点
+                else if (equaln(ea, this.StartAngle))//this起点对终点
                 {
-                    if (eaAllan < allAn)
+                    if (saAllan < allAn)
                         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;
+                }
+                else if (this.ParamOnCurve(this.GetParamAtAngle(sa)))
+                {
+                    if (eaAllan < saAllan)
+                        this.ConverToCircle();
                     else if (eaAllan > allAn)
                         this.EndAngle = ea;
-
                     return true;
                 }
-                if (eaAllan < saAllan && saAllan < allAn)
+                else if (this.ParamOnCurve(this.GetParamAtAngle(ea)))
                 {
-                    this.ConverToCircle();//圆
+                    this.StartAngle = sa;
                     return true;
                 }