Take Guangzhou airport express bus line 1 at Baiyun International Airport to get to Guangzhou CAAC Ticket Office (near to Guangzhou Railway Station). Then take D trains from Guangzhou to Shenzhen. When you arrive at Shenzhen Railway Station, get out and pass Luohu Border to Reach Hong Kong.
Airport express line 1 info:
PS: here is another option for you (from Guangzhou to Hong Kong). You can take direct bus at some hotels like Guangzhou Huatai Hotel, Huahai Building, Hotel Canton, Yingbin Hotel, Guangzhou Hotel, New Tianhe Hotel, President Hotel.
There are many buses at Guangzhou Hotel. You may go there to take the bus.
Ticket price: CNY 100 (Guangzhou to Disneyland) CNY 120 (Guangzhou to Ocean Park) CNY 200 (Guangzhou to Hong Kong Airport).
Round trip (Guangzhou to Hong Kong) costs CNY 140.
For details, please call 020- 833
Easy Bus Transportation from Hong Kong Airport to Your Hotel
Hong Kong Airport (HKK) to Airport Express Train to ...
on a train to Chek Lap Kok Hong Kong inter Airport