The former Masters champion began the day locked in a tie with Gregory Bourdy with both men on 13-under.
However, the Frenchman bogeyed his first hole on the way to a two-over 74 while Schwartzel fired 10 birdies with just two dropped shots, his first of this week's tournament, as he shot a second 64 in a row to go with his first round 67.
Despite his impressive lead Schwartzel is not taking anything for granted ahead of the final round.
"As a golfer you don't like to think like that. It's a nice comfort and I'd rather be 10 ahead than nine ahead. Whatever lead you can build is great. We've all see what can happen in this game. I don't want to think about it," he told reporters.
Schwartzel enjoyed a superb front nine as he made the turn at four-under for the round after just 31 strokes on the picturesque par-72 lay-out bordering the Kruger National Park.
He then fired four consecutive birdies from the 12th before chalking up another birdie on the 541-yeard par five 18th.
Despite his fine scoring Schwartzel said he was not that pleased with his driver and it was his putting that had been responsible for his position at the end of day three.
"I don't think I'm hitting my driver very well but I'm hitting my three-wood well. I seem to go for that and I'm hitting it really long, so it's working out for me. Once I get into position then my iron play is good.
"Probably the biggest thing of all is that I'm converting the putts," he said.
Schwartzel added that as long as he could keep the ball in play off the tee he had a chance of picking up birdies.
"You don't need you're A-game to score well. There's a big difference between flushing the golf ball and scoring. I'm not flushing it, but I'm scoring well. When you flush it you feel a lot less pressure. When you're not hitting it well it doesn't mean that you're going to score worse, you've just got to work so much harder to get the ball down in play," he said.
Bourdy was alone in second place on 11-under with a group of three - Sweden's Kristoffer Broberg, South Africa's Branden Grace and Briton Steve Webster - a shot further back.
South Africa's Keith Horne enjoyed a special moment with a second consecutive hole-in-one on the 192-yard par three 12th, winning a luxury German car for his achievement.