how do i get to south railway station from guangzhou airport before 6 am?

You can take MTR Line 3 (North extension) from the airport to Jiahe Wanggang and then transfer to Metro Line 2 to South Station. The first departure of MTR Line 3 (North extension) is at 6:02. If you can’t take this, then you can take a taxi to Jiahe Wanggang to take Metro Line 2.

thanks helen! but then i'm arriving in guanzhou airport past midnight and metro is not yet open. can a taxi ferry my straight to south station? thanks again

Yes, taxi is the best way at night!