In fact, Beijing South Railway Station is also very convenient. Take Line 4 directly to Beijing South Railway Station and don't get off.
Bus route: Daxing Line of Metro Line 4 → Metro Line 9, the whole journey is about11.2km..
1. Walk about 270 meters from Peking University and arrive at the East Gate Station of Peking University.
2. Take Daxing Line of Metro Line 4, pass 5 stops and arrive at National Library Station.
3. Take Metro Line 9, pass 4 stops and arrive at Beijing West Railway Station.