you take the bus from Beijing Muxiyuan Long-distance Bus Station.
the bus departs at 18:00 and arrives at around 04:00 the next morning.
the bus fare is around CNY 180
took a bus from 北郊长途汽车站(bei jiao chang tu qi che zhan)~ cost 200RMB~
This the bus station I left out of : 北郊长途汽车站.
Its in the north of the city, fairly central – a little west of the Olympic village area.