diff --git a/app/api/canvas/[id]/route.ts b/app/api/canvas/[id]/route.ts
index 791d578..5d5a721 100644
--- a/app/api/canvas/[id]/route.ts
+++ b/app/api/canvas/[id]/route.ts
@@ -38,7 +38,7 @@ export async function GET(
   }
 }
 
-// 更新画布
+// 更新画布（支持 upsert：如果不存在则创建）
 export async function PUT(
   request: NextRequest,
   { params }: { params: Promise<{ id: string }> }
@@ -53,30 +53,58 @@ export async function PUT(
     const body = await request.json();
     const { title, description, thumbnail, canvasData } = body;
 
-    const updateData: any = { updatedAt: new Date() };
-    if (title !== undefined) updateData.title = title;
-    if (description !== undefined) updateData.description = description;
-    if (thumbnail !== undefined) updateData.thumbnail = thumbnail;
-    if (canvasData !== undefined) updateData.canvasData = canvasData;
-
-    const [updatedProject] = await db
-      .update(canvasProject)
-      .set(updateData)
+    // 先检查画布是否存在
+    const [existingProject] = await db
+      .select()
+      .from(canvasProject)
       .where(
         and(
           eq(canvasProject.id, id),
           eq(canvasProject.userId, session.user.id)
         )
-      )
-      .returning();
+      );
 
-    if (!updatedProject) {
-      return NextResponse.json({ success: false, error: '画布不存在' }, { status: 404 });
+    if (existingProject) {
+      // 更新现有画布
+      const updateData: any = { updatedAt: new Date() };
+      if (title !== undefined) updateData.title = title;
+      if (description !== undefined) updateData.description = description;
+      if (thumbnail !== undefined) updateData.thumbnail = thumbnail;
+      if (canvasData !== undefined) updateData.canvasData = canvasData;
+
+      const [updatedProject] = await db
+        .update(canvasProject)
+        .set(updateData)
+        .where(
+          and(
+            eq(canvasProject.id, id),
+            eq(canvasProject.userId, session.user.id)
+          )
+        )
+        .returning();
+
+      return NextResponse.json({ success: true, data: updatedProject });
+    } else {
+      // 创建新画布（使用指定 ID）
+      const [newProject] = await db
+        .insert(canvasProject)
+        .values({
+          id, // 使用指定的 ID
+          userId: session.user.id,
+          title: title || '未命名画布',
+          description,
+          canvasData: canvasData || {
+            nodes: [],
+            edges: [],
+            viewport: { x: 0, y: 0, zoom: 1 },
+          },
+        })
+        .returning();
+
+      return NextResponse.json({ success: true, data: newProject });
     }
-
-    return NextResponse.json({ success: true, data: updatedProject });
   } catch (error) {
-    console.error('更新画布失败:', error);
+    console.error('更新/创建画布失败:', error);
     return NextResponse.json({ success: false, error: '更新画布失败' }, { status: 500 });
   }
 }