diff --git a/src/DatabaseServices/Circle.ts b/src/DatabaseServices/Circle.ts
index 7bf417858..672474cc4 100644
--- a/src/DatabaseServices/Circle.ts
+++ b/src/DatabaseServices/Circle.ts
@@ -5,11 +5,11 @@ import { ColorMaterial } from '../Common/ColorPalette';
 import { RenderType } from '../GraphicsSystem/Enum';
 import { Factory } from './CADFactory';
 import { CADFile } from './CADFile';
-import { Entity } from './Entity';
+import { Curve } from './Curve';
 
 
 @Factory
-export class Circle extends Entity
+export class Circle extends Curve
 {
     constructor(center?: Vector3, radius?: number)
     {
@@ -145,4 +145,4 @@ export class Circle extends Entity
         file.Write(this.m_Radius);
     }
     //#endregion
-}
\ No newline at end of file
+}
diff --git a/src/DatabaseServices/Curve.ts b/src/DatabaseServices/Curve.ts
new file mode 100644
index 000000000..868676fae
--- /dev/null
+++ b/src/DatabaseServices/Curve.ts
@@ -0,0 +1,36 @@
+import { Vector3 } from 'three';
+
+import { Factory } from './CADFactory';
+import { Entity } from './Entity';
+
+
+/**
+ * 曲线的基类,子类请实现以下方法.
+ * 
+ * @export
+ * @class Curve
+ * @extends {Entity}
+ */
+@Factory
+export abstract class Curve extends Entity
+{
+    constructor()
+    {
+        super();
+    }
+    get StartPoint(): Vector3 { return; }
+    get StartParam(): number { return; }
+    get EndPoint(): Vector3 { return; }
+    get EndParam(): number { return; };
+    get Area(): number { return; }
+    get IsClose(): boolean { return; }
+
+    GetPointAtParam(param: number): Vector3 { return; }
+    GetPointAtDistance(distance: number): Vector3 { return; }
+    GetDistAtParam(param: number): number { return; };
+    GetDistAtPoint(pt: Vector3): number { return; }
+    GetFistDeriv(param: number | Vector3): number { return; }
+
+    GetSplitCurves(param: number[] | number): Array<Curve> { return; }
+    Extend(newParam: number) { }
+}
diff --git a/src/DatabaseServices/Line.ts b/src/DatabaseServices/Line.ts
index 51182c33f..f2c5c5eef 100644
--- a/src/DatabaseServices/Line.ts
+++ b/src/DatabaseServices/Line.ts
@@ -6,10 +6,10 @@ import { ColorMaterial } from '../Common/ColorPalette';
 import { RenderType } from '../GraphicsSystem/Enum';
 import { Factory } from './CADFactory';
 import { CADFile } from './CADFile';
-import { Entity } from './Entity';
+import { Curve } from './Curve';
 
 @Factory
-export class Line extends Entity
+export class Line extends Curve
 {
     private startPoint: Vector3;
     private endPoint: Vector3;
@@ -119,4 +119,4 @@ export class Line extends Entity
     }
 
     //#endregion
-}
\ No newline at end of file
+}