把下面函数代码放入 functions.php（注：函数随手写的，可能不够精简）

/**
* get subpage previous/next page link by zwwooooo
*/
function subpage_nav_link($prevText='', $nextText='') {
global $post;
if ( !$post->post_parent ) return null; //如果不是子页面返回Null
$args = array(
'sort_order' => 'ASC',
'sort_column' => 'menu_order',
'child_of' => $post->post_parent,
'post_type' => 'page'
);
$pages = get_pages($args);
$num = count($pages);
$i = 0;
$index = -1;
foreach ($pages as $page) {
if ($page->ID == $post->ID) {
$index = $i;
break;
}
++$i;
}
if ($i == 0) {
$prev = '';
$next = $pages[$index+1];
} elseif ($i == $num-1) {
$prev = $pages[$index-1];
$next = '';
} else {
$prev = $pages[$index-1];
$next = $pages[$index+1];
}
if ($prev) {
if ($prevText) {
if ( substr_count($prevText, '%title') > 0 ) {
$explode = explode('%title', $prevText);
$prevText = $explode[0] . get_the_title($prev->ID) . $explode[1];
}
} else {
$prevText = get_the_title($prev->ID);
}
$prevlink = '<a class="previous-page-link" href="' . get_page_link($prev->ID). '">' . $prevText . '</a>';
}
if ($next) {
if ($nextText) {
if ( substr_count($nextText, '%title') > 0 ) {
$explode = explode('%title', $nextText);
$nextText = $explode[0] . get_the_title($next->ID) . $explode[1];
}
} else {
$nextText = get_the_title($next->ID);
}
$nextlink = '<a class="next-page-link" href="' . get_page_link($next->ID). '">' . $nextText . '</a>';
}
return array($prevlink, $nextlink);
}