The 28 year-old, who finished 24-under-par overall after his three-under round, had begun the day with a 10-shot advantage over Frenchman Gregory Bourdy and never looked in any danger as he reached the turn at level-par for his round.
A two-hour delay for thunderstorms at the Leopard Creek Country Club followed, but the former U.S. Masters champion returned to the 10th hole and cruised to victory with three further birdies and no bogeys.
Sweden's Kristoffer Broberg ended up second.
"I thought I started off well today and through the first six holes I had an opportunity on every hole," Schwartzel told reporters.
"I hit good putts that didn't go in. Then the three-putt on eight put a stop to things and Gregory started to make some birdies. Then it got down to seven shots and that to me was as close as I wanted it to be.
"I was happy to make that birdie on nine just to pull the momentum back in my favour, because seven shots around this course is catchable. After the rain delay we came back and I played some nice, solid golf and put myself back in the driver's seat."
Last week Schwartzel claimed an 11-stroke victory at the Thailand Golf Championship on the Asian Tour, his first win in 20 months, and he dazzled the crowds once again at home as he stormed clear of his rivals for the second week in succession.
"This doesn't happen often. You don't see it happen often. For me it's nice after last week," Schwartzel added.
"Last week I got that win by a big margin, and normally when you come back the next week it's hard to put up the same show.
"That's pleasing and what I keep talking about is consistency. It's back where I like it to be."
Those behind Schwartzel were always fighting it out for second place and for much of the day it looked as though Bourdy was on course for the runners-up cheque.
However, a calamitous double-bogey on the final hole meant he fell back to 11-under and the Frenchman had to settle for a four-way share of third place with Andy Sullivan, Garth Mulroy and Scott Jamieson, while Broberg earned sole possession of second as his final round of 70 took him to 12-under.
Another Swede enjoyed a memorable moment on the day, as Magnus A. Carlsson's seven-iron found the cup for a hole-in-one on the 12th hole.
South Africa's Keith Horne had carded an ace on the very same hole in successive days on Friday and Saturday, but Carlsson's earned the prize of a brand new car as it came during the final round of play.