最终这样做（例如，如果相关帖子的ID为5）：

function filter_posts($query) {
  if ( $query->is_category() && $query->is_main_query()) {
     $this_category = get_queried_object();
     if (0 == $this_category->parent) // Category has no parent
        $query->set(\'post__not_in\', array(\'5\'));
  }
}
add_action(\'pre_get_posts\', \'filter_posts\');