A brisk half-century from AB de Villiers put South Africa in position to declare their second innings.
South Africa and India face off in the ICC World Twenty20 semi-final in Dhaka on Friday.
The Aussies were set 448 for victory after Graeme Smith declared on 270 for 5 before lunch.
JP Duminy made 123 with AB de Villiers scoring 116.
JP Duminy, AB de Villiers, Wayne Parnell and Vernon Philander put SA at St George's Park on Friday.
A win against the Bizhub Highveld Lions on Friday could see them automatically qualify for the final.