The 25-year-old Feng, winner of the 2012 LPGA Championship and here in the same year, shot a final-round two-under par 70 to finish on 19-under par 269 for the four days.
That tally was two shots shy of the record winning total of 21-under par in 2012, but good enough for a massive five-shot winning margin.
Spain’s Carlota Ciganda, who won the Order of Merit crown in 2012, made a spectacular up-and-down from the back bunker of the 18th hole to finish second at 14-under par, one better than Germany’s Caroline Masson, who shot the day’s best round of five-under par 67 to climb up to third place.
England’s Charley Hull wrapped up the Order of Merit crown, just one year after she won the Rookie of the Year award.
The 18-year-old became the youngest winner of the most prestigious title in the LET, which also gives her the bragging rights of being called the European number one for the season.
Hull shot an even-par 72 on Saturday to finish tied for fifth at 10-under par, while her closest competitor, France’s Gwladys Nocera, who needed to be inside the top-four to have a chance of overtaking her, was tied 11th in the end at 280.
Wales’ Amy Boulden (285) won the Rookie of the Year title when she finished ahead of Scotland’s Sally Watson (291), while Nicole Broch Larsen of Denmark (278) could only manage a tied fifth place instead of solo second.
FENG VERY HAPPY
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Feng, whose 70 on Saturday was her worst round of the tournament, made two bogeys on the back nine against four birdies overall.
"I was told there is only one player who has won this tournament twice, and that is Annika Sorenstam and me. Any time you are on any list along with Annika, you know you have done pretty good," said Feng.
"I did not have much pressure on me today as I was five shots ahead, so I just set myself a target of 22-under.
"I thought I would beat my own record, and that it would be a total that would be difficult for anybody else in the field to catch. It did not happen, but I am very happy still.”
Hull, who needed to recover from a poor start to the day when she made a double bogey on the tough par-4 opening hole of the Majlis course, was delighted to follow her Rookie of the Year title with the European number one spot.
"Yeah, that's good. I think I wanted to do that because you only got one chance to do that. I am happy," she said.
"The win in Morocco (her only professional win earlier this year) is definitely bigger, but winning the Order of Merit is a pretty good thing as well.
"I didn't really think about it coming into this week. Just on the back nine today, and then I told myself 'don't make any silly mistakes'."
World number 12 Anna Nordqvist of Sweden shot a 70 to finish fourth at 276.