Australia took a further four wickets in the afternoon session in Perth to reduce South Africa to 141-7.
Resuming on 63-3, South Africa quickly lost their fourth wicket when Hashim Amla was run out by David Warner for 11.
Less than an over later, Australia snapped up their fifth wicket when AB De Villiers was caught by Michael Clarke off the bowling of John Hastings.
The tourists were in disarray and they fell to 75-6 as Dean Elgar was dismissed for a duck when he edged to Matthew Wade off a Mitchell Johnson delivery.
South Africa finally displayed some resistance when Robin Peterson joined Faf Du Plessis at the crease and they put on a 57-run partnership before Peterson lost his wicket for 31.
Australia's pressure late on in the session failed to pick up another wicket but they will expect to have their opponents in the field by the time close of play arrives on day one.
