请尝试将以下代码添加到主题中functions.php 文件

function remove_add_to_cart_option( $purchasable, $product ){
    if( $product->get_price() == 0 )
        $purchasable = false;
    return $purchasable;
}
add_filter( \'woocommerce_is_purchasable\', \'remove_add_to_cart_option\', 10, 2 );

 /*
 * Override via functions.php
 **/
 if (!function_exists(\'woocommerce_template_loop_add_to_cart\')) {
 function woocommerce_template_loop_add_to_cart() {
    global $product;
    if ( ! $product->is_in_stock() || ! $product->is_purchasable() ) return;
    woocommerce_get_template(\'loop/add-to-cart.php\');
  }
}

希望它能帮助你！