Having compiled the fastest triple century in Test history on Friday, Sehwag then passed his own record for most runs scored by an India batsman in a single Test innings by adding the single he needed to his overnight score of 309.
Rahul Dravid also scored a century for the hosts, but the Proteas made their own mark with the ball, effecting something of a collapse as the hosts were all out for 627 at tea - a lead of 87 runs.
Neil McKenzie then struck a half century in the evening session to give his side a lead of 44 and put the match on the brink of a draw.
India had started the day 72 runs short of the Proteas' first-innings total of 540 but with nine wickets in hand.
Sehwag quickly scored the run he needed to set a new milestone of 310 when he flicked Dale Steyn's first delivery of the day to long leg for a single.
Finally he dismissed for 319 when he got a thick outside edge to a makhaya ntini delivery. Thus the sehwag paradise on chepauk and eventhough his knock match going almost into a drawn stage. We will wait and see what going to happen in the last day.