According to Baidu map, you can take Metro Line 7 and transfer from Guangzhou South Railway Station to Metro Line 3 to Dashi Subway Station. The specific process is as follows:

1. Walk from Guangzhou South Railway Station120m, get on at Guangzhou South Railway Station, take Metro Line 7 (University South) and get off at Hanxi Changlong Station.

2. Transfer to the station and walk 230 meters, get on the bus at Hanxi Changlong Station, take Metro Line 3 at 1 station (in the direction of Tianhe Bus Terminal), get off at Dashi Station and walk 10 meters to your destination.