I'm coming from shenyang to beijing by train then have to go to airport . suggest metro train route

If you arrive at BJ Station, you can take Shuttle Bus line 3 to the airport; or take metro line 2 and transfer to airport express at Dongzhimen, and get off at the airport.

If you arrive at South Station, you can take Shuttle Bus line 2 there; or take metro line 4 and transfer to line 2 at Xuanwumen, then transfer to airport express at Donghzimen.