McIlroy and Donald -- the world's top two ranked golfers -- are at 17-under 199 after 54 holes of the European Tour's select season-ending event.
They are three strokes ahead of Charl Schwartzel, who shot 67 Saurday, and Louis Oosthuizen, who turned in a third-round 68. Branden Grace (70 Saturday) and Joost Luiten (67) are tied for fifth at 12-under.
Marc Warren, who was tied with McIlroy and Donald for the lead after the second round, needed two late birdies to get back to even for the day Saturday and is among seven players tied for seventh at 11-under.
Donald is yet to have a bogey in the tournament. He was 4-under on the front nine Saturday and his two second-nine birdies came on par 5s.
McIlroy opened the day with a bogey -- his second of the week -- but birdies at Nos. 3 and 6 allowed him to make the turn at 1-under. He had back-to-back birdies at Nos. 11 and 12 before catching Donald with an eagle at the 636-yard, par-5 14th.
While Donald edged ahead with his 18th-hole birdie, McIlroy also birdied the 620-yard hole, for a share of the third-round lead.