Transportation between Beijing and Hong Kong

Air
Beijing is located at northeast China, while Hong Kong is at south China. Flight distance is 1,980km (1,230mi), so this is the best way to travel between these two cities. There are almost 50 direct flights (in one way) daily, and flight time is about 3:40 hours. From Beijing departures are between 6:50 and 21:00 on every 20-60 minutes, while from Hong Kong departures are between 7:50 and 22:50 on every 20-60 minutes. There are few flights at 3:00 departing from Beijing. Return flight usually cost from about CNY2,000 (economy class) or more, but there are often discounted tickets.
You can book flights on: www.ctrip.com

Train
You can choose between overnight or high-speed daily train for train travel between Beijing and Hong Kong.

Overnight trains are recommended option, because they are comfortable, direct, and cheap. It is sleeper train and you can save money for hotel bill. Travel time is about 24 hours, and tickets are CNY1,200/820/507. Drawback is the fact that they departure on every second day.

High-speed trains shorten trip to 11-12 hours in total. They departure daily, but these are not direct trains, and you will have to make stop in Shenzhen. You will have to cross border between China and Hong Kong on foot. High-speed trains are not as cheap as sleeper trains are. It is day time trip and basically you will have to spend all day in train. Even if it is high-speed train, it is still at least 11 hours trip without sleeper berths, so it is not as comfortable as overnight train is.

Overnight trains (BJ to HK train number Z97; HK to BJ train number Z98; 24 hours travel time) operate between Beijing West Railway Station (北京西站; departure at 13:00 on even dates in January, April, May, August, November, December, and on odd dates in February, March, June, July, September, October) and Hung Hom Station in Kowloon Hong Kong ( 紅磡站; departure at 15:15 on even dates in odd dates in January, April, May, August, November, December, and on even dates in February, March, June, July, September, October). You can take deluxe sleeper (CNY1,200/HK$1,190), soft sleeper (CNY820/HK$935) or hard sleeper (CNY507/HK$586). All sleeper berths in this train are recommended.

High-speed trains operates daily on Beijing-Shenzhen-Hong Kong route.

Beijing-Hong Kong: from Beijing West Railway Station to Shenzhen North Railway Station (深圳北站) you can take either train number G71 which travel from 7:40 to 17:53, or train number G79 which travel from 10:00 to 18:35. You can choose between business (CNY2,920), 1st (CNY1,480) and 2nd (CNY936) class seats.

From Shenzhen North Railway Station take metro to Futian Checkpoint Station (福田口岸站). It is last station on southern end of Longhua line. From Futian Checkpoint Station you will have to walk to cross the border. Once you arrive in Hong Kong you can take Hong Kong metro at Lok Ma Chau Station (落馬洲) to anywhere you like in Hong Kong.

Hong Kong-Beijing: take Hong Kong metro to the Lok Ma Chau Station. Cross the border by foot and once you enter the China, take metro from Futian Checkpoint Station to Shenzhen North. For trip from central Hong Kong to Shenzhen North Railway Station, including metro rides and border crossing, you will need at least 3 hours.

From Shenzhen North Railway Station to Beijing West Railway Station you can take either train number G72 which travel from 7:53 to 18:21, or train number G80 which travel from 11:29 to 21:47. You can choose between business (CNY2,920), 1st (CNY1,480) and 2nd (CNY936) class seats.

Don’t forget to be at the train station at least 90 minutes before departure. For crossing the border between China and Hong Kong you will need from 20 minutes or more depending on queues.
You can check timetables and buy train tickets online on:
www.chinahighlights.com
www.china-diy-travel.com