1. Take bus 9 18 to Dongzhimen from Jingping Expressway.
Method: Take 957 Express 2 to Liujiayao in Daxing, then take Line 5 and transfer to Line 2 to Dongzhimen. Next is the bus lobby. Look for 9 18 expressway 1 (take Jingping expressway). Because it is the main station, there must be a seat. The whole journey takes about 2 hours and 20 minutes.
40 minutes (957)+20 minutes (subway) +60 minutes (9 18)+20 minutes (walking) = 140 minutes.
2. Take 9 18 Jingping Expressway to Sanyuanqiao.
Methods: Take the 957 express 2 to Sanyuanqiao in Daxing, get off the bridge and walk about 800 meters to 9 18 Sanyuanqiao Station. Take the 9 18 express 1 (Jingping Expressway) or 9 18 (if you take the airport expressway, you have to pass Shunyi, which is 40 minutes slower than Jingping Expressway). Probably didn't take this jump route, it was all at the main station. So you have to stand for an hour to get to Pinggu. The whole journey takes about 2 hours and 20 minutes. If you take the 9 18 airport expressway, it may take about 3 hours.
60 minutes (957)+ 15 minutes (walk) +60 minutes (9 18)= 135 minutes
3. Long-distance bus at Daxing Long-distance Station
Methods: There is a green minibus opposite Daxing Long-distance Station and at the entrance of Cannongji Community, with the word Pinggu written on it. The bus passes through Tongzhou and Shunyi for three and a half hours, two or three times a day, one at 9 am and one in the afternoon 1. I don't know if I can hold on after sitting for 3 hours, mainly because I have to stop and go to Tongzhou, which is smooth and tired!
I don't know if it is detailed enough. Have a nice trip. Baidu Maps