What is the latest train from Hongkong to Guangzhou? I arrive at HK airport in the evening.

As I know, it operates about every 1 hour from Hong Kong to Guangzhou between 07:30 and 19:15. And it will cost you about 70 minutes and 190HKD for 1st cabin per person. One important thing is you need to arrive in the station 45 minutes before departure to handle exit formalities. You had better go earlier to ensure catch the last one.