diff --git a/backend/app/controller/UserController.php b/backend/app/controller/UserController.php
index f73cf64..5544782 100644
--- a/backend/app/controller/UserController.php
+++ b/backend/app/controller/UserController.php
@@ -3,6 +3,7 @@
 namespace app\controller;
 
 use app\model\User;
+use app\model\UserSystemMapping;
 use Webman\Http\Request;
 use Webman\Http\Response;
 
@@ -130,4 +131,36 @@ class UserController extends BaseController
             'page_size' => $pageSize,
         ]);
     }
+
+    /**
+     * 获取用户在指定系统的映射ID
+     */
+    public function systemMapping(Request $request): Response
+    {
+        $userId = $this->getUserId($request);
+        $systemCode = $request->get('system', 'fdesk');
+
+        // 获取用户信息以获取公司ID
+        $user = User::find($userId);
+        if (!$user) {
+            return $this->error('用户不存在');
+        }
+
+        // 查询系统映射
+        $mapping = UserSystemMapping::active()
+            ->bySystem($systemCode)
+            ->where('user_id', $userId)
+            ->where('company_id', $user->company_id)
+            ->first();
+
+        if (!$mapping) {
+            return $this->error('未找到系统映射信息，请联系管理员配置');
+        }
+
+        return $this->success([
+            'system_code' => $mapping->system_code,
+            'system_user_id' => $mapping->system_user_id,
+            'system_user_name' => $mapping->system_user_name,
+        ]);
+    }
 }
diff --git a/backend/app/model/UserSystemMapping.php b/backend/app/model/UserSystemMapping.php
new file mode 100644
index 0000000..f3893fd
--- /dev/null
+++ b/backend/app/model/UserSystemMapping.php
@@ -0,0 +1,89 @@
+<?php
+
+namespace app\model;
+
+use support\Model;
+
+class UserSystemMapping extends Model
+{
+    protected $table = 'user_system_mapping';
+
+    /**
+     * 可填充字段
+     */
+    protected $fillable = [
+        'user_id',
+        'company_id',
+        'system_code',
+        'system_user_id',
+        'system_user_name',
+        'status',
+    ];
+
+    protected $casts = [
+        'user_id' => 'integer',
+        'company_id' => 'integer',
+        'status' => 'integer',
+        'created_at' => 'datetime',
+        'updated_at' => 'datetime',
+    ];
+
+    /**
+     * 关联用户
+     */
+    public function user()
+    {
+        return $this->belongsTo(User::class, 'user_id');
+    }
+
+    /**
+     * 关联公司
+     */
+    public function company()
+    {
+        return $this->belongsTo(Company::class, 'company_id');
+    }
+
+    /**
+     * 获取有效的映射
+     */
+    public function scopeActive($query)
+    {
+        return $query->where('status', 1);
+    }
+
+    /**
+     * 根据系统代码查找
+     */
+    public function scopeBySystem($query, string $systemCode)
+    {
+        return $query->where('system_code', $systemCode);
+    }
+
+    /**
+     * 根据公司ID查找
+     */
+    public function scopeByCompany($query, int $companyId)
+    {
+        return $query->where('company_id', $companyId);
+    }
+
+    /**
+     * 根据外部系统用户ID查找
+     */
+    public function scopeBySystemUserId($query, string $systemUserId, string $systemCode = 'fdesk')
+    {
+        return $query->where('system_code', $systemCode)
+            ->where('system_user_id', $systemUserId);
+    }
+
+    /**
+     * 获取用户在指定系统的映射
+     */
+    public function scopeUserMapping($query, int $userId, int $companyId, string $systemCode = 'fdesk')
+    {
+        return $query->where('user_id', $userId)
+            ->where('company_id', $companyId)
+            ->where('system_code', $systemCode);
+    }
+}
diff --git a/backend/config/route.php b/backend/config/route.php
index ad9643a..4cdfa3d 100644
--- a/backend/config/route.php
+++ b/backend/config/route.php
@@ -36,6 +36,7 @@ Route::group('/api/v1/user', function () {
     Route::get('/menu', [app\controller\UserController::class, 'menu']);
     Route::get('/companies', [app\controller\UserController::class, 'companies']);
     Route::get('/list', [app\controller\UserController::class, 'list']);
+    Route::get('/system-mapping', [app\controller\UserController::class, 'systemMapping']);
     Route::post('/switch-company', [app\controller\UserController::class, 'switchCompany']);
     Route::post('/change-password', [app\controller\UserController::class, 'changePassword']);
 })->middleware($authMiddleware);
diff --git a/docs/DATABASE_SCHEMA.md b/docs/DATABASE_SCHEMA.md
index 552f472..f65f29a 100644
--- a/docs/DATABASE_SCHEMA.md
+++ b/docs/DATABASE_SCHEMA.md
@@ -1,8 +1,8 @@
 # 数据库结构文档
 
-**版本**: 1.1.0
-**更新时间**: 2026-03-01
-**状态**: 线上稳定版本
+**版本**: 1.1.1
+**更新时间**: 2026-03-03
+**状态**: 开发中
 
 ---
 
@@ -358,6 +358,34 @@
 
 ---
 
+### 15. user_system_mapping - 用户系统映射表
+
+用于将本项目用户ID映射到外部系统（如fdesk、ERP、CRM等）的用户ID。
+
+| 字段 | 类型 | 必填 | 默认值 | 说明 |
+|------|------|------|--------|------|
+| id | bigint unsigned | ✓ | AUTO_INCREMENT | 记录ID |
+| user_id | bigint unsigned | ✓ | | 本项目用户ID |
+| company_id | bigint unsigned | ✓ | | 公司ID |
+| system_code | varchar(50) | ✓ | fdesk | 系统代码（如：fdesk, erp, crm） |
+| system_user_id | varchar(100) | ✓ | | 外部系统用户ID |
+| system_user_name | varchar(100) | | | 外部系统用户名（冗余字段） |
+| status | tinyint | ✓ | 1 | 状态：1=有效，0=无效 |
+| created_at | timestamp | ✓ | CURRENT_TIMESTAMP | 创建时间 |
+| updated_at | timestamp | ✓ | CURRENT_TIMESTAMP | 更新时间 |
+
+**索引**:
+- PRIMARY KEY (`id`)
+- UNIQUE KEY `uk_user_company_system` (`user_id`, `company_id`, `system_code`)
+- KEY `idx_system_user_id` (`system_code`, `system_user_id`)
+- KEY `idx_company_id` (`company_id`)
+
+**说明**:
+- 同一用户在同一公司下对应一个外部系统只能有一条记录
+- 支持多个外部系统的映射关系
+
+---
+
 ## 📊 表关系图
 
 ```
@@ -368,6 +396,8 @@ users (1) ----< (N) user_feishu_apps
   +----> companies (1) ----< (N) company_feishu_apps
          |
          +----> user_sn (N)
+         |
+         +----> user_system_mapping (N)
 
 users (1) ----< (N) business_trip
   |                            |
@@ -419,5 +449,5 @@ users (1) ----< (N) business_trip
 ---
 
 **维护人**: 开发团队
-**最后更新**: 2026-03-01
-**版本**: 1.1.0 (线上稳定版)
+**最后更新**: 2026-03-03
+**版本**: 1.1.1