Is bus 867 still running to Matianyu great wall ?

Yes, it is still in service. It departs from Dongzhimen to the great wall directly at 10:00 and 12:00. And it returns to Hongluosi scenic area at 14:00 and 15:00. Then from Hongluosi, every 30 mins, there is a bus back to Dongzhimen.
The bus station is about 650 yards walking distance from the Exit H of Dongzhimen subway station, near Dongwaixie Street.