we will be arriving11.30 pm. need advise to travel from xian airport to sofitel hotel in reminin sq.

You can take airport shuttle bus line 3 to the railway station. The service hours of this line are from 08:00am to 00:00pm. After arriving, take a taxi to your hotel directly. The taxi fare is about CNY 10.
If you don't catch this line, you can take airport shuttle bus line 1 to Xishaomen Airport Business Hotel. This line opens from 7:20 am to the last flight arrival. Then just take a taxi to the hotel. The taxi fare is about CNY 15.

The best way to the destination is get the taxi after you arrive, because it is so cold and it's midnight, safer, save time.