After missing a short birdie putt at 18 with a chance to set the course record, Casey came back more than an hour later and birdied the hole to beat Wilson in the playoff.
Wilson bogeyed the extra hole after hitting into two greenside bunkers. He had been one shot ahead of Casey's clubhouse lead before a bogey at the 17th dropped him into a tie.
Both players finished at 13-under-par 275 for the tournament -- Casey after a course record-tying, 7-under 65 and Wilson after a final-round 69 at Shenzhen Golf Club.
Barry Lane, also of England, shot a 68 and ended alone in third place at 12- under-par 276.
Overnight leader Ross Fisher rounded out a strong showing by Englishmen by shooting an even-par 72 to finish in a tie for fourth place. He was joined at minus-11 by Thailand's Chawalit Plaphol, who shot a 71.
Casey reached 13 under with a bogey-free final round. But his day was filled with squandered opportunities, like the eagle putt he missed at the par-5 12th and the 7-foot birdie try he rolled wide at the 15th.
'I was a little bit frustrated with the putts that didn't go in today,' said Casey, 'but I gave myself so many chances that I didn't feel like I was under that much pressure.'
Neither of those misses came close to the disappointment at 18, where he pushed a simple 3-foot putt wide to finish his final round with a par.
'I thought maybe I'd blown it at the last,' Casey admitted. 'I played a wonderful round of golf today, so I can't complain. I didn't make the putts in regulation, but it was nice to get the chance in a playoff. I didn't think I'd have it, and I capitalized.'
With Casey in the clubhouse, Wilson rallied past the leader by stringing together four straight birdies from the 12th to reach 14 under. But after scrambling for par at 16, he missed a 12-foot putt at 17 to fall into a tie for the lead.
At the 18th Wilson landed just over the green on his second shot, but couldn't make birdie after chipping into the center of the large green.
Both players then had a shot at redemption when they returned to the 539-yard, par-5 18th. And it was Casey who made the best of his second chance after spending more than an hour in the clubhouse and on the practice green
After Wilson found the fairway with his drive, Casey hit into the first cut of rough off the tee. But some pressure was taken off his shoulders when Wilson knocked a fairway wood into the first of two bunkers guarding the right side of the green.
After Casey landed an iron shot in the middle of the green, he watched as Wilson popped his third shot into another bunker.
Wilson basically had to hole his second bunker shot for a realistic chance to win, but he landed it on the fringe. Only needing to two-putt for the victory, Casey left himself with a knee-knocker for birdie.
But he calmly rolled in the short putt for his fifth European Tour title and second playoff win in eight months after beating Paul McGinley at the TCL Classic in March.
That victory also came in China.
'Two wins, two playoffs in China -- that's something special,' said Casey, who pocketed $216,660 for first place.
Fisher and Lane were also flirting with Casey's lead for a while, but both dropped back with costly mistakes on the back nine. Lane's double bogey at 15 left him two shots off the lead at that point, and Fisher fell behind with a bogey at the 14th.
Sitting in the clubhouse, Casey watched as players challenged his position. And when it was clear that a playoff was in the making, he didn't mind the short rest he had been given.
'It was enough time to go and cool down and collect myself,' he said. 'It was the right amount of time...a very long wait would have been difficult.'
Ireland's Peter Lawrie fired a final-round 69 and finished alone in sixth place at 10-under. Thongchai Jaidee (67), Jyoti Randhawa (70), Miles Tunnicliff (71) and China's Lian-Wei Zhang (72) ended one stroke further back in a tie for seventh.