您可以覆盖woocommerce templates 将它们放在主题中。覆盖，例如。form-billing.php 模板，将其放置在yourtheme/woocommerce/checkout/form-billing.php 目录

您还可以添加filter 覆盖表单字段呈现函数。甚至overwrite 整个功能。

要添加新字段，请参阅WooCommerce documentation.

我正在粘贴文档中的代码，以添加字段，而不是只将答案保留在链接中：

/**
 * Add the field to the checkout
 */
add_action( \'woocommerce_after_order_notes\', \'wpse_287663_custom_checkout_field\' );

function wpse_287663_custom_checkout_field( $checkout ) {

    echo \'<div id="custom_checkout_field"><h2>\' . __(\'My Field\') . \'</h2>\';

    woocommerce_form_field( \'field_name\', array(
        \'type\'          => \'text\',
        \'class\'         => array(\'my-field-class form-row-wide\'),
        \'label\'         => __(\'Fill in this field\'),
        \'placeholder\'   => __(\'Enter something\'),
        ), $checkout->get_value( \'field_name\' ));

    echo \'</div>\';
}

/**
 * Process the checkout
 */
add_action(\'woocommerce_checkout_process\', \'wpse_287663_custom_checkout_field_process\');

function wpse_287663_custom_checkout_field_process() {
    // Check if set, if its not set add an error.
    if ( ! $_POST[\'field_name\'] )
        wc_add_notice( __( \'Please enter something into this new shiny field.\' ), \'error\' );
}

/**
 * Update the order meta with field value
 */
add_action( \'woocommerce_checkout_update_order_meta\', \'wpse_287663_custom_checkout_field_update_order_meta\' );

function wpse_287663_custom_checkout_field_update_order_meta( $order_id ) {
    if ( ! empty( $_POST[\'field_name\'] ) ) {
        update_post_meta( $order_id, \'My Field\', sanitize_text_field( $_POST[\'field_name\'] ) );
    }
}

/**
 * Display field value on the order edit page
 */
add_action( \'woocommerce_admin_order_data_after_billing_address\', \'wpse_287663_custom_checkout_field_display_admin_order_meta\', 10, 1 );

function wpse_287663_custom_checkout_field_display_admin_order_meta($order){
    echo \'<p><strong>\'.__(\'My Field\').\':</strong> \' . get_post_meta( $order->id, \'My Field\', true ) . \'</p>\';
}