只用WordPress定时任务去生成sitemap.xml，这样比网上很多方法是在保存、发布文章时生成xml好一些，不会造成处理文章卡的现象。在WordPress主题文件functions.php中或者使用Code Snippets插件添加自定义代码：

// 判断定时计划是否存在
if ( ! wp_next_scheduled( \'sitemap_xml\' ) ) {
  wp_schedule_event( time(), \'twicedaily\', \'sitemap_xml\' ); // 每天两次
}
add_action( \'sitemap_xml\', \'sitemap_xml_func\' );
 
// 定时计划执行函数
function sitemap_xml_func() {
  // 获取文章数量
  $count_posts = wp_count_posts();
  if ( $count_posts ) {
    $published_posts = $count_posts->publish;
    $sitemap_num = $published_posts / 3000; // 每个xml文件最多包含3000篇文章
    $sitemap_num = ceil($sitemap_num);
 
    // 创建xml文件
    for ($i = 1; $i <= $sitemap_num; $i++) {
      $postsForSitemap = get_posts(array(
        \'numberposts\' => 3000,
        \'orderby\' => \'modified\',
        \'post_type\'  => array(\'post\'),
        \'order\'    => \'DESC\',
        \'offset\' => 3000 * ($i - 1)
      ));
      $sitemap = \'<?xml version=\"1.0\" encoding=\"UTF-8\"?>\';
      $sitemap .= \'<urlset xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\">\';
      foreach($postsForSitemap as $post) {
        setup_postdata($post);
        $post_url = get_permalink($post->ID);
        $post_date = get_the_modified_date( \'c\',$post->ID );
 
        $sitemap .= \'<url>\'.
              \'<loc>\'. $post_url .\'</loc>\'.
            \'<lastmod>\'.  $post_date .\'</lastmod>\'.
              // \'<lastmod>\'. $postdate[0] .\'</lastmod>\'.
          // \'<changefreq>monthly</changefreq>\'.
          \'</url>\';
      }
      $sitemap .= \'</urlset>\';
      $fp = fopen(ABSPATH . \"sitemap-\".$i.\".xml\", \'w\');
      fwrite($fp, $sitemap);
      fclose($fp);
    }
 
    // 创建sitemap.xml文件
    $sitemap_all = \'<?xml version=\"1.0\" encoding=\"UTF-8\"?>\';
    $sitemap_all .= \'<sitemapindex xmlns=\"http://www.sitemaps.org/schemas/sitemap/0.9\">\';
    for ($i = 1; $i <= $sitemap_num; $i++) {
      $sitemap_all .= \'<sitemap>\'.
            \'<loc>\'. get_bloginfo(\'url\') .\'/sitemap-\'.$i.\'.xml</loc>\'.
            \'<lastmod>\'. date(\'c\') .\'</lastmod>\'.
          \'</sitemap>\';
    }
    $sitemap_all .= \'</sitemapindex>\';
    $fp = fopen(ABSPATH . \"sitemap.xml\", \'w\');
    fwrite($fp, $sitemap_all);
    fclose($fp);
  }
}