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.
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.
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.
England's Justin Rose, the Olympic gold medallist in 2016 and a former major champion, finished tied 18th at 13 under.