The American, who fired a dazzling 11-under-par 59 on Saturday to grab the outright lead, finished 22 under for victory in Asia's oldest professional golf tournament.
The 34-year-old Reed, who is among a number of big-name players to have jumped over to Saudi-backed LIV Golf, carded six birdies against two bogeys for a final-round 66 at Fanling.
It was Reed's first win on the Asian Tour.
"Nothing like coming to a place that I know pretty well and love the golf course," he said.
"I love how it makes me think about golf shots and you have to be creative around this place."
Reed, the champion at Augusta in 2018 and a nine-time winner on the US PGA Tour, sealed victory ahead of defending champion Ben Campbell of New Zealand in outright second.
Reed shot a rare 59 in the third round but preferred lies were played so the feat does not stand officially.
"To be able to come out and play the way like I did on the weekend... it always helps shooting 59 yesterday but the biggest thing, the hardest part, was today."
England's Justin Rose, the Olympic gold medallist in 2016 and a former major champion, finished tied 18th at 13 under.
