如果有人想清理这一切，那就更好了，但它完成了任务：）

如果我理解正确，您需要用户的ID，是吗？

有关的详细信息$wp_user_query 查看这篇文章，它是我编写此代码的部分资源：http://www.mattvarone.com/wordpress/list-users-with-wp_user_query/

// List Users
add_action("admin_init", "users_meta_init");

function users_meta_init(){
  add_meta_box("users-meta", "User Select", "users", "post", "normal", "high");
}

function users(){
  global $post;
  $custom = get_post_custom($post->ID);
  $users = $custom["users"][0];

    // prepare arguments
$user_args  = array(
// search only for Authors role
\'role\' => \'Author\',
// order results by display_name
\'orderby\' => \'display_name\'
);
// Create the WP_User_Query object
$wp_user_query = new WP_User_Query($user_args);
// Get the results
$authors = $wp_user_query->get_results();
// Check for results
if (!empty($authors))
{
    // Name is your custom field key
    echo "<select name=\'users\'>";
    // loop trough each author
    foreach ($authors as $author)
    {
        // get all the user\'s data
        $author_info = get_userdata($author->ID);
        $author_id = get_post_meta($post->ID, \'users\', true);
        if($author_id == $author_info->ID) { $author_selected = \'selected="selected"\'; } else { $author_selected = \'\'; }
        echo \'<option value=\'.$author_info->ID.\' \'.$author_selected.\'>\'.$author_info->first_name.\' \'.$author_info->last_name.\'</option>\';
    }
    echo "</select>";
} else {
    echo \'No authors found\';
}

}

// Save Meta Details
add_action(\'save_post\', \'save_userlist\');

function save_userlist(){
  global $post;

if (defined(\'DOING_AUTOSAVE\') && DOING_AUTOSAVE) {
    return $post->ID;
}

  update_post_meta($post->ID, "users", $_POST["users"]);
}