add_action('woocommerce_product_options_general_product_data','my_custom_fields');

function my_custom_fields() {
    $field = array(
       //This ID will be use on the _postmeta table as key_name
       'id' => 'my_custom_message',//Text that goes inside the label tag
       'label' => 'Message:',//This text will appear on the description column
       'description' => 'This is a custom message not part of WooCommerce',//Boolean that determines the display of the description
       'desc_tip' => true,//Standard html input placeholder
       'placeholder' => 'Type a message',);
    woocommerce_wp_text_input($field);
}

add_action('woocommerce_process_product_meta','save_my_custom_fields');

function save_my_custom_fields($post_id) {
    update_post_meta(
        $post_id,'my_custom_message',esc_attr($POST['my_custom_message'])
    );
}

请尝试使用上面的代码，并将id字段替换为所需的参数