Hi, what identification do I need to book and travel on a train? I will only have a photocopy of my

Yes, a coy of your passport is ok for you to book a train ticket in China.

But do I need my passport to check in when I get to the train station? Also do you know if a photocopy of my passport is ok for booking and checking in?

Ministry of Railways in China takes Real-Name Train Ticket Policy now, so you need to book and buy train tickets with a valid certification like ID card or passport or their copy. Generally, you can board your train only with the train ticket on which there is your passport number.