You can easily buy train tickets for others in several ways:
At the station: Visit the ticket counter and present the passenger's valid ID (original or a copy of their ID card, passport, or residence permit for Hong Kong, Macao, and Taiwan residents).
Automated Ticket Machines: If you have the passenger's original ID card, you can often use it directly at an automated ticket vending machine to purchase their ticket.
Online (12306.cn or App)
1. Register and verify your own ID on the official China Railway ticket service platform (12306.cn) or the "铁路12306" app (which has an English option in the settings).
2. Once logged in, add the person you're buying for to your "My Passengers" list. You'll need their name, valid ID document type, and ID number.
3. After their ID information is "verified" or "ready to be verified", you can select them when booking tickets.