高考顺利的英文表达可以有以下几种：

Good luck on your Gaokao.

Good luck for your exam and do your best.

You can do this. Best of luck.

It’s your lucky day.

Sail through.

Wish you a great success in the College Entrance Examination.

Wish you could do a great job in the College Entrance Examination.

pass the college entrance exam （高考） with flying colors.

这些表达都是常见且合适的，可以根据具体场合选择合适的祝福语。