from hong kong airport to Guangzhou by train

You arrive so late. At that time, the through trains between Hung Hom and Guangzhou East have been out of service. And the last direct bus from HKIA to Guangzhou leaves at 22:15, so you will miss it too.

As for your case, it would be best to stay near HKIA for a night. In the next morning, take a direct bus to go or take shuttle bus no. A21 to Hung Hom and transfer to a train to your destination.