您可以通过wp_nav_menu_args 滤器

假设你有一个这样的主题。。。

<?php
wp_nav_menu(array(
    \'theme_location\'   => \'second_level\',
    \'depth\'            => 2, // how many levels to show
    // prolly some other stuff here
));

<?php
add_filter(\'wp_nav_menu_args\', \'wpse87565_change_depth\');
function wpse87565_change_depth($args)
{
    if (!empty($args[\'theme_location\']) && \'second_level\' === $args[\'theme_location\']) {
        $args[\'depth\'] = 1;
    }

    return $args;
}