The overview of Beijing: 

Beijing is also an important gateway to Tibet by train. It is the capital city and well-linked by international flights with many foreign big cities. So, most foreigners will choose to come to Tibet from Beijing.
Destinations
Train No.
Depart
Arrive
Runtime
Distance
(km)
Fare in CNY
Hard
sleeper
Soft
sleeper
Beijing(west) to Lhasa
Z21
20:00
12:45
(3rd day)
40h45m
3753
720
1144
Lhasa to Beijing(west)
Z22
15:50
08:28
(3rd day)
40h45m
Frequency: Every day
Note: The train ticket costs we listed in the table are net ticket costs, but most of the time it is very difficult to get the train tickets as there is a huge number of visitors taking the train every day, so a certain amount of services will be added to get the tickets from a local ticket agent, the exact amount of service fees will different based on the season, so please contact our trip advisor for the exact cost of the tickets.

Beijing West Train Station (火车西站)

Address: Located near the West 3rd Ring Road, the station is only 8km from the Forbidden City,
Phone: 010-51826273 or 010-51521673
Ticket Booking Hotline: 12306
Metro to There:  Line 7 or Line 9
Bus to There: No. 3, No. 9, No. 21, No. 40, No. 50, etc.
Taxi to there: Taking a taxi from the airport to Beijing West Train station cost around CNY150 and takes about 50 min.
Note: Please make sure that you have a copy of the Tibet Travel Permit to board the train.