diff --git a/app/Models/Dealer.php b/app/Models/Dealer.php
index 217fca61..023c8b1c 100644
--- a/app/Models/Dealer.php
+++ b/app/Models/Dealer.php
@@ -21,7 +21,8 @@ class Dealer extends Model
         'lvl' => DealerLvl::class,
         'is_sale' => 'bool',
         'is_manager' => 'bool',
-        'pay_info'=>JsonArray::class,
+        'pay_info' => JsonArray::class,
+        'contracted_lvl_at' => 'datetime',
     ];
 
     protected $fillable = [
@@ -30,8 +31,21 @@ class Dealer extends Model
         'is_sale',
         'is_manager',
         'pay_info',
+        'contracted_lvl_at',
     ];
 
+    /**
+     * {@inheritdoc}
+     */
+    protected static function booted()
+    {
+        static::creating(function ($dealer) {
+            if ($dealer->last_upgrade_at === null) {
+                $dealer->last_upgrade_at = now();
+            }
+        });
+    }
+
     public function user()
     {
         return $this->belongsTo(User::class, 'user_id');
@@ -64,9 +78,9 @@ class Dealer extends Model
     /**
      * 属于此经销商的升级日志
      */
-    public function lvlUpgradeLogs()
+    public function upgradeLogs()
     {
-        return $this->hasMany(DealerLvlUpgradeLog::class, 'user_id', 'user_id');
+        return $this->hasMany(DealerUpgradeLog::class, 'user_id', 'user_id');
     }
 
     public function getLvlTextAttribute()
@@ -135,4 +149,35 @@ class Dealer extends Model
             return $item->dealer;
         })->all();
     }
+
+    /**
+     * 变更等级
+     *
+     * @param \App\Enums\DealerLvl $lvl
+     * @param string|null $remark
+     * @return void
+     */
+    public function changeLvl(DealerLvl $lvl, ?string $remark = null)
+    {
+        if ($this->lvl === $lvl) {
+            return;
+        }
+
+        $before = $this->lvl;
+
+        if ($lvl->value < DealerLvl::Contracted) {
+            $this->contracted_lvl_at = null;
+        } elseif ($lvl->value >= DealerLvl::Contracted->value && $this->contracted_lvl_at === null) {
+            $this->contracted_lvl_at = now();
+        }
+
+        $this->lvl = $lvl;
+        $this->save();
+
+        $this->upgradeLogs()->create([
+            'before_lvl' => $before,
+            'change_lvl' => $lvl,
+            'remark' => $remark,
+        ]);
+    }
 }
diff --git a/app/Models/DealerUpgradeLog.php b/app/Models/DealerUpgradeLog.php
new file mode 100644
index 00000000..56ef885c
--- /dev/null
+++ b/app/Models/DealerUpgradeLog.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace App\Models;
+
+use App\Enums\DealerLvl;
+use Illuminate\Database\Eloquent\Model;
+
+class DealerUpgradeLog extends Model
+{
+    protected $casts = [
+        'before_lvl' => DealerLvl::class,
+        'change_lvl' => DealerLvl::class,
+    ];
+
+    protected $fillable = [
+        'user_id',
+        'before_lvl',
+        'change_lvl',
+        'remark',
+    ];
+}
diff --git a/database/migrations/2022_01_17_160300_add_contracted_lvl_at_to_dealers_table.php b/database/migrations/2022_01_17_160300_add_contracted_lvl_at_to_dealers_table.php
new file mode 100644
index 00000000..7e98eee9
--- /dev/null
+++ b/database/migrations/2022_01_17_160300_add_contracted_lvl_at_to_dealers_table.php
@@ -0,0 +1,32 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+class AddContractedLvlAtToDealersTable extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::table('dealers', function (Blueprint $table) {
+            $table->timestamp('contracted_lvl_at')->nullable()->comment('成为签约的时间');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::table('dealers', function (Blueprint $table) {
+            $table->dropColumn(['contracted_lvl_at']);
+        });
+    }
+}