how to buy a train ticket from Guangzhou to Xiamen

Dear Christinato,
Thank for you enquiry!
You can buy the ticket by yourself at a railway station in China with your original passport. But chinese railway tickets are available 20 days in advance, and many tickets are in large demand. So you may not able to get your ticket at the railway station.
Alternatively, you can book with us through our online booking service. We will inform your via emails after we successfully book the ticket for you. Then you can have your paper tickets printed out at any one railway station by presenting your original passport. Or you can choose our delivery service to have your ticket sent a hotel you reserved.