OMalley, who has only won one European Tour event in the past 13 years, led a group of four who shot 4-under 68s: Swedens Henrik Stenson, Indias Jeev Milka Singh, Oliver Wilson of England and Finlands Mikko Ilonen.
The 42-year-old OMalley had six birdies and one bogey to lead the $2.3 million jointly sanctioned European and Asian Tour event at the Tomson Shanghai Pudong course.
There is certainly a premium on accuracy off the tee and the ball is rolling too so it is not playing as long as it can, OMalley said. On the fairways, you couldnt ask for a better playing surface so the course is well-suited to my game.
Fellow Australian and former world No. 1 Greg Norman was among 34 players to break par, finishing the opening round of a rare tournament appearance at 1 under along with local hope Zhang Lian-wei and former U.S. Open champion Michael Campbell.
I thought it should have been better, Norman said. I played well except for a couple of holes but outside of that, I concentrated well and putted well and didnt make anything.
Stenson, who is trying to reclaim leadership of the European Order of Merit from U.S. Masters winner Trevor Immelman, had six birdies and a bogey.
Singh compensated for a mediocre round off the tee and fairways with a strong performance on the greens, requiring only 23 putts over the 18 holes.
Ilonen had an eagle on the seventh hole.
Australias Scott Hend was sixth at 3-under 69 after having his old clubs sent to him from the United States, replacing the set he used when missing the cut in Beijing last week. Hend picked up six strokes in an eight-hole spurt before a double bogey on his third-to-last hole cost him a share of the lead.
South Africas Retief Goosen was among those to shoot even par 72 in his opening round, along with Germanys Martin Kaymer and Spains Miguel Angel Jimenez.