Hi, I'd like to know which long distance bus station is the nearest to Hangzhou Airport?

The nearest one is Passenger Tranport Center at No. 3339, East Desheng Road, Jiubao Town, Jianggan District. It is about 17 miles (27km) away from the airport.
You can take a coach from Ningbo South Bus Station and arrive at Passenger Tranport Center first. The buses are available from 7:10 to 19:45, and the trip takes about 2 hours. The fare is CNY 65 per person.
After arriving, take a shuttle bus to the airport directly. The buses are available from 6:40 to 22:55, and the fare is CNY 20 per person.
Hope helpful!