As you arrived in Harbin Taiping Airport at midnight, you don't have much choice. You can take a Taxi at the picking up point, it is across the road from the airport exit. Drivers will either try and negotiate a price or tell you they will go by the meter, either way it's in their favor. I can tell you a reasonable price for a taxi at that hour will cost you between 150-180 RMB including toll fee of 20RMB. Drivers will agree a price and then try to charge you extra for the Toll!

If you go be meter, keep your eye on the meter as they have been known to change very quickly!

Make sure the taxi you board is a proper taxi in the queue and not through touts since it will probably pass 12 midnight by the time you board the taxi.

If you would not want to the hassle of getting into an argument with the Taxi driver in the middle of the night. I would suggest you book a Uber or DiDi Driver by advance which probably cost RMB 150 total.