Answered by ZUPAN | Aug. 30, 2019 13:29
You can indeed take a direct train from Hong Kong Hung Hom railway station to Beijing West railway station. This train is eligible for 144 hour visa free transit scheme. Of course, before your departure with the mentioned train, you will have to decide and book a flight ticket for a third country destination, for example:
Hong Kong - Beijing (mainland China) - Ulaanbaatar (Mongolia)
So, having a ticket that will bring you to the third country or eligible territory (Taiwan and Macau) before your boarding on the train in Hong Kong is a must.
I will assume that you have such a ticket... Upon your arrival at Beijing West railway station, you will approach 144 hour TWOV counter where you will fill out the blue form and present your onward ticket that should be in hard copy (a printout of your e-ticket in reality). You are also advised to book your first overnight in Beijing in advance because in the mentioned form there are a couple of questions regarding your accommodation. After a short inspection, you will get a sticker in your passport and you will be allowed to exit the railway station.
Please, have in mind that this train departs every other day, so you should plan accordingly.