I'm in Prudential Hotel HK,want to go to Guangzhou by train.

From your hotel, you are suggested to take Tsuen Wan Line from Jordan Station to Tsim Sha Tsui Station. Then transfer to West Rail Line to Hung Hom Station, Exit B2. After that, walk to north and arrive at Hung Hom Railway Station. The duration is about 25 mins. It costs 4.4 HKD per person.
There are many direct trains that can take you to Guangzhou. The schedules are from 07:25 to 20:01. It takes around 2 hours on the way. The ticket fare of first class seat is CNY183 and VIP seat is CNY218. :)