使用pre\\u get\\u posts可能有效。您能否尝试以下类似的方法，并告诉我是否满足您的需要：

function search_filter($query) {
  if ( !is_admin() && $query->is_main_query() ) {
    if ($query->is_search) {
      $query->set(\'post_type\', array( \'post\', \'movie\' ) );
      //Should do some sanitation on $GET too
      if(isset($_GET[\'author\'])){    //Change to your field dropdown name
        $query->set(\'meta_key\', \'author\'); //change to custom field name
        $query->set(\'meta_value\', $_GET[\'author\']);   
      }
      else if(isset($_GET[\'pubyear\'])){    
        $query->set(\'meta_key\', \'pubyear\');
        $query->set(\'meta_value\', $_GET[\'pubyear\']);   
      }
    }
  }
}

add_action(\'pre_get_posts\',\'search_filter\');