McDowell coped well with a fluctuating breeze and thick rough at Sheshan Golf Club to fire a five-under-par 67 after two late bogeys spoilt his card.
He headed a group of six players on 69 that included current U.S. Open champion Martin Kaymer and consistent American Rickie Fowler.
World number two Adam Scott of Australia was a further shot back after a 70, but it was a miserable day for recent U.S. PGA Tour FedEx Cup winner Billy Horschel, who flung his ball into a water hazard in disgust at his final hole after shooting an error-strewn 80.
McDowell is not the longest of hitters and he prefers courses where birdies are hard to come by, so he was delighted when he arrived in Shanghai to find plenty of thick rough on a track that traditionally had yielded low scores.
“A big key to this course is driving the ball well (and) I drove it very well today,” the world number 17, who finished third here last year, told reporters.
“I think I missed only one fairway (and that) set up a few opportunities. The greens are in fantastic shape and I actually putted very well, so seven under par through 12 holes was a beautiful start.
“I dropped a couple coming in but all in all, very, very pleased with five under on what I thought was a reasonably tricky day.”
McDowell, the 2010 U.S. Open champion, said he did not expect the winning score to be better than 12-under on Sunday.
It was a good start for another of Europe’s Ryder Cup winning side with team mate Kaymer showing little sign of rust.
This is the German’s first official tournament since September team event. He was even par after 10 holes, but remained patient and was rewarded with a strong finish.
“I just kept telling myself, you enjoy the golf course so much, and you will have plenty of birdie chances, so you just need to wait,” he said. “Fortunately, it turned out well.”
But the day did not turn out so well for American Kevin Stadler (wrist) and Canadian Graham DeLaet (back), who both withdrew during the round.
American Jason Dufner incurred a one-stroke penalty when he absent-mindedly picked up his ball to clean it on the 18th hole, apparently forgetting that the “lift, clean and place” rule was not being used. He shot 72.
Dufner played last week’s CIMB Classic in Malaysia where the rule was used due to the damp course conditions.
(Editing by Patrick Johnston)