Stenson held a four-stroke lead after finishing the rain-interrupted second round earlier Saturday, and sat at 17-under 199 heading into Sundays final round.
Robert Karlsson of Sweden shot 67 and trailed Stenson, who had seven birdies in his bogey-free round.
Rory Sabbatini of South Africa battled all day to stay in touch, but repeatedly missed crucial putts and ended with a double bogey-6 on the 18th after his approach reached a bunker. Sabbatini remained in third place after shooting 72, 11 shots off the lead.
American Ryder Cup star Kenny Perry had seven birdies, but added three bogeys for a 68. That was enough to vault him into fourth place ahead of Englands Lee Westwood (70).
Stenson opened the tournament with a course-record 63 on Thursday. He said his string of birdies helped his confidence.
There was a little bit of fighting earlier on, but from nine onwards I obviously started making a lot of birdies and that kind of gets you going, Stenson said. I hit of lot of good putts that finished four or five inches short on line, so I guess I could have made even a few more, but overall Im absolutely not complaining about that.
Defending champion Trevor Immelman tallied a 69, but trails the leader by 15 shots.