I am landing at 20.45 please help how to reach suzhou from pudong airport

Oh, the last schedule of the direct long-distance bus is at 21:00. I'm afraid that you cannot catch it.
So you can take airport shuttle bus line 5 to get to Main Railway Station first. The duration is about 80 mins. Then take high-speed train to arrive at SZ Railway Station. The available train schedules are 22:08 and 22:33.