Chengdu and Xian tour

I am planning to visit Xian and CD in August/ Sept ,I will go to Xian first then from there will go to CD by train. Is there any problem for me? How many hours it will take? Since in late August is not a peak season,Is it necessary to prebook the train tickets? Understand to fly from Xian to CD is a very good option?

Your reply is very much appreciated.


Wong c c