我找到了这段代码，它可以工作：

<?php get_header(); ?>
<div id="job-listings">
<?php
            $category = get_the_category();
            $theName = $category[0]->name;
            $theChild = $category[0]->cat_ID;
$subcats = get_categories(\'child_of=\' . $theChild);
    foreach($subcats as $subcat) {
    echo \'<h3>\' . $subcat->cat_name . \'</h3>\';
    echo \'<ul>\';
    $subcat_posts = get_posts(\'cat=\' . $subcat->cat_ID);
    foreach($subcat_posts as $subcat_post) {
        $postID = $subcat_post->ID;
    echo \'<li>\';
    echo \'<a href="\' . get_permalink($postID) . \'">\';
    echo get_the_title($postID);
    echo \'</a></li>\';
    }
    echo \'</ul>\';
    } ?>
 </div>
 <?php get_footer(); ?>