Where is the bus station going to HK airport from Chungking mansion?thank you.

You can take bus no.A21 at Haiphong Road, Nathan Road, get off at the airport directly. From your hotel, you can walk northwest around 250 yards to find the pick-up station. It's beside the Golden Crown Guesthouse.
The duration is about 65 mins. The ticket fare is 33 HKD per person.