I want to visit Zhenbeitai of Great Wall from Xi'an in one day of course, what can I do?

Ilaria, I am afraid that you can't finish the trip in one day. This part of the wall is located in Yulin. Xian is around 700 kilometers from Yulin. It takes around 6 hours and 40 minutes by the fast train. So you need take a night train from Xian to Yulin first. Then you can take a taxi to reach the wall. If you prefer to go by public bus, you can take no. 10 bus from the square of Yulin Railway Station to get off at Zhanghang (中行) station, walk around 170 meters to find Guang Ji Da Sha (广济大厦) station. There you can change no.3 bus to that tower.