diff --git a/src/Builder.php b/src/Builder.php
index afe49f9..6075f7d 100644
--- a/src/Builder.php
+++ b/src/Builder.php
@@ -474,8 +474,15 @@ public function multiAggregate($options, $extra)
             $groups['_id'][$field] = '$' . $field;
         }
 
-        foreach ($aggregate as $fun => $field) {
-            $groups[$field . '_' . $fun] = ['$' . $fun => '$' . $field];
+        // 支持对于一个聚合操作添加多个字段
+        foreach ($aggregate as $fun => $fields) {
+            foreach ($fields as $field) {
+                if ($fun == 'count') {
+                    $groups[$field . '_count'] = ['$sum' => 1];
+                } else {
+                    $groups[$field . '_' . $fun] = ['$' . $fun => '$' . $field];
+                }
+            }
         }
         $pipeline = [
             ['$match' => (object)$this->parseWhere($options['where'])],
diff --git a/src/Query.php b/src/Query.php
index e78f9d2..f172673 100644
--- a/src/Query.php
+++ b/src/Query.php
@@ -494,7 +494,8 @@ public function count()
     /**
      * 多聚合操作
      *
-     * @param array $aggregate 聚合指令, 可以聚合多个参数, 如 ['sum' => 'field1', 'avg' => 'field2']
+     * @param array $aggregate 聚合指令, 可以聚合多个参数
+     *              如 ['sum' => ['field1', 'field2'], 'avg' => ['field2', 'field3']]
      * @param array $groupBy 类似mysql里面的group字段, 可以传入多个字段, 如 ['field_a', 'field_b', 'field_c']
      * @return array 查询结果
      */