The highest ranked player in the field at world No 5, DeChambeau pulled ahead from the chasing pack with three birdies in his first three holes, and then almost assured himself of his fourth win in last nine starts with an eagle on the 10th hole and a birdie on the 11th.
At that stage, he was six ahead of the field. After making his only bogey of the day on the difficult par-4 12th hole, he added further birdies on the 13th, 14th and 17th holes to finish on eight-under par 64 for the day and 24-under for the four rounds, also the lowest in the history of the tournament.
The previous biggest margin of victory was six by Ernie Els over Greg Norman in 1994. The old record for lowest tournament aggregate was set last year by Li Hao-tong (23-under par).
England's Matt Wallace (68), the most successful player on the European Tour last season with three wins, made a stunning birdie after spraying his tee shot wide right into the waste area on the 18th, to break out of a logjam on 16-under par and finish solo second at 17-under par 271.
Two more Englishmen, Ian Poulter and Paul Waring had set the target by finishing on 16-under par with rounds of 64. They were later matched by 2017 champion Sergio Garcia (66) and 2001 winner Alvaro Quiros (both Spain) to tie for third place.
South Africa's Justin Harding shot the best round of the day in the morning - a nine-under par 63 elevating him to tied seventh place at 15-under par in a group that also included Lee Westwood (67) of England.
fourth round scores from the European Tour's Dubai Desert Classic on
Sunday at the par-72 Majlis course of Emirates Golf Club (GBR & IRL
264 – Bryson DeChambeau (USA) 66-66-68-64
271 – Matt Wallace 70-64-69-68
272 – Ian Poulter 67-71-70-64, Paul Waring 67-70-71-64, Sergio Garcia (ESP) 66-70-70-66, Alvaro Quiros (ESP) 69-64-71-68
273 – Justin Harding (RSA) 70-68-72-63, Lee Westwood 67-70-69-67,
Jason Scrivener (AUS) 67-67-71-68, Thorbjorn Olesen (DEN) 69-67-68-69,
Lucas Herbert (AUS) 69-63-72-69
274 – Shane Lowry 69-67-71-67, An Byeong-hun (KOR) 70-68-68-68, Ernie Els (RSA) 68-65-70-71, Li Haotong (CHN) 67-67-67-73
275 – Romain Wattel (FRA) 68-70-70-67, Tommy Fleetwood 68-70-68-69,
Matthew Fitzpatrick 65-70-70-70, Kalle Samooja (FIN) 66-70-68-71
276 – Pablo Larrazabal (ESP) 72-66-74-64, Tapio Pulkkanen (FIN)
68-73-69-66, Alexander Bjork (SWE) 68-70-72-66, Romain Langasque (FRA)