Can i go to terracota warriors by subway in Xian

I am afraid that the metro can not take you to the terrcotta army.
You can go to take the Bus 306 (Tourism Line 5) at local Railway Station East Square to reach that attraction directly.

Thanks! From the airport I was planning to take airport shuttle bus to xian railway station drom where I can take bus 5 to go to Terracota. Is there any other short route? I saw in the net that the bus can be obtained from the east square of the xian railway station. How do I reach the east square?

There is no other short route.
The airport shuttle bus stops very close to the East Square, so you can easily walk to take bus 5. If you cannot find the east square, you can ask the shuttle bus driver and they will tell you.