I arrive changsha airport at 00.20 am and i want to go to hotel near west bus station by taxi .

Based on your landing time, you can take airport shuttle bus line 1 and get off at Main Railway Station first. The bus will operate until the last flight arrival. It costs CNY15.5 per person. The duration is around 40mins. Then take a taxi to the hotel nearby the West Coach Station. The cab fare is CNY 40 at night.