The American hit an imperious eight-under 64 on the final day at Emirates Golf Club to finish on 24-under, seven shots clear of the field in a record winning margin.
World no. 5 DeChambeau smashed through his final round with an eagle, seven birdies and a sole bogey to post the lowest 72-hole score in the tournament’s history.
DeChambeau had begun his final round a shot clear and quickly increased his lead with a 20-foot birdie on the 1st before further gains at the 2nd. and 3rd.
He put himself into an almost unassailable six-shot lead with a 10-foot eagle putt at the 10th and another birdie at the 11th.
At the 12th an errant shot into a bush meant a dropped shot but DeChambeau bounced straight back with birdies on the 13th and 14th.
He missed further chances to reach the tournament record at the 15th and 16th but putted in for a final birdie on the seventeenth and secured par on the 18th for the win.
“Today I was happy with my game. I executed a lot of great shots,” DeChambeau, 25, told the European Tour website.
“Today was a pleasure. It was obviously a lot of fun to be able to finally hoist an international trophy, I’m so happy about that.
“I was trying to shoot 25-under today and missed it by one, but I’m happy with the results for sure.”
Wallace closed his round with back-to-back birdies to lift himself out of the pack and into second place.
Compatriots Paul Waring and Ian Poulter also enjoyed impressive final rounds of 64 to finish in the four-man tie for third, with Spaniards Garcia and Quiros alongside them after rounds of 66 and 68.
2018 champion Li Haotong from China had started the day just one shot behind DeChambeau but tailed off with a 1-over round of 73 to finish on 14-under alongside South African Ernie Els who narrowly missed out on 300th career top-ten finish.