Is it possible to go to Huashan Mountain after visiting the Terracotta Warriors Museum?

Dear Erick, there is no direct bus from the museum to Huashan.
There are 3 ways recommended to you:
1. First come back Xi'an Railway station and then take the the bus or train to Huashan.
2. First take a taxi to Weinan Bus Station and then take the bus to Huashan.
3. Take a taxi or hire a car to Huashan directly.