1. Take Metro Line 5, pass 16 and arrive in dongdan station.
2. Walk for about 250 meters, and then transfer to Metro 1.
3. Take the subway 1 line, pass 4 stops and arrive at Xidan Station.
4. Walk about 400 meters and transfer to Daxing Line of Metro Line 4.
5. Take Daxing Line of Metro Line 4, pass 4 stops and arrive at Beijing South Railway Station.
6. Walk about180m to Beijing South Railway Station.
The above is the specific route to Beijing South Railway Station. I hope it helps you.