The 22-year-old star from Northern Ireland made seven birdies in another bogey-free round on Lake Malaren’s Jack Nicklaus-designed Masters course to finish at 18-under 198.
“Another good day on the course! Excited to have a chance to get another win this year!” McIlroy tweeted, adding the hashtag “itsbeentoolong.”
South Korea’s Noh Seung-yul was 14 under after a 67.
Ian Poulter (67) and Hunter Mahan (68) were 11 under, second-ranked Lee Westwood (70) and Geoff Ogilvy (66) were another stroke back, and Robert Karlsson (72), Padraig Harrington (73) and Y.E. Yang (68) were 6 under.
Louis Oosthuizen struggled in the overcast conditions, shooting a 76 to finish at 4 under. The 2010 British Open champion had a double bogey on the par-5 13th and made four bogeys.
The 30 players are vying for the $2 million first prize, the richest in golf. All the top players are getting appearance money, and last place pays $25,000. Because the International Management Group-run event isn’t sanctioned by a major tour, it doesn’t have world-ranking points.
The World Golf Championships-HSBC Champions is next week at nearby Sheshan International.