My flight will arrived Xi'an at 21.35 (local time), Our hotel is in Sahara Youth Inn/Muslim Quarter.

According to your landing time, you are adviced to take airport shuttle bus Xishaomen Line to get to Xishaomen Airport Business Hotel. The operating hours is until the last flight arrival. So don't worry. The ticket fare is CNY 25 per person. And it takes around an hour in usual time.
After arriving, just take a taxi to arrive at the destination directly. The cab fare would be about CNY 13 at night.