我不是百分之百确定，但似乎注册链接是在general-template.php 在里面wp-includes. 查看函数wp_register. 这里有一个名为register 可用于过滤wp-login.php 出来

/**
 * Display the Registration or Admin link.
 *
 * Display a link which allows the user to navigate to the registration page if
 * not logged in and registration is enabled or to the dashboard if logged in.
 *
 * @since 1.5.0
 * @uses apply_filters() Calls \'register\' hook on register / admin link content.
 *
 * @param string $before Text to output before the link (defaults to <li>).
 * @param string $after Text to output after the link (defaults to </li>).
 * @param boolean $echo Default to echo and not return the link.
 */
function wp_register( $before = \'<li>\', $after = \'</li>\', $echo = true ) {

    if ( ! is_user_logged_in() ) {
        if ( get_option(\'users_can_register\') )
            $link = $before . \'<a href="\' . site_url(\'wp-login.php?action=register\', \'login\') . \'">\' . __(\'Register\') . \'</a>\' . $after;
        else
            $link = \'\';
    } else {
        $link = $before . \'<a href="\' . admin_url() . \'">\' . __(\'Site Admin\') . \'</a>\' . $after;
    }

    if ( $echo )
        echo apply_filters(\'register\', $link);
    else
        return apply_filters(\'register\', $link);
}

add_filter(\'register\', \'wpse28495_wpRegister\');
function wpse28495_wpRegister($link) {
    if(!is_user_logged_in()) {
        $link = \'<a href="\' . site_url(\'my-login.php\') . \'">\' . __(\'Register\') . \'</a>\';
    }

    return $link;
}