how long to transfer from terminal 3 to terminal 2 at PEK?

There are free shuttle buses available between these two terminals, and the bus ride is 10-15 mins.

Thank you very much for the answer, sarah. I would be coming into terminal 3 from ulaanbaatar and would have to take another flight from terminal 2 in 2 hours time. would be flying into beijing on air china and my bags wont be checked in all the way. so i would have to get my bags go through passport control get out of terminal 3 and move to terminal 2. Am not sure if i could do it in 2 hours and make it to board the next flight. Do you have any advice on this?

If it is an international to international transfer, your time is enough. Just hurry up.

If it is an international to domestic transfer, you need at least 160 mins. I'm afraid you have to change another flight of later schedule.