I would have my flight from Chongqing International airport at 2 am. How should I go from the city?

Don't worry. According to your landing time, you can still take bus no.01 to Shangqing Temple. This bus line will operate until 30 mins after the last flight arrival. So you can catch it. It costs CNY 10 per person with the duration of around 40 mins. Hope helpful!

Thank you for your reply. but my flight will leave Chongqing Airport at 2am .

Sorry. Generally speaking, you need to arrive at the airport at least 2 hours in advance before the departure. You can take the shuttle bus from Shangqing Temple. The buses depart from 05:30 to 21:00 with the frequency of around half an hour. The ticket fare is CNY 10 per person. It also takes around 40 mins.
Or you can also take a taxi from downtown area to the airport. :)

Thank you ^^