Feng went round in six under par on Sunday to finish on 15 under for the tournament, edging out American Gerina Piller.
The Chinese player picked up six birdies in a flawless round, getting off to a flying start with four in her first six holes and then finishing strongly with two more at the 15th and 17th.
Piller, one of three overnight leaders, carded a three-under 69 in the fourth round, with bogeys at the second and seventh giving her too much work to do on the back nine.
Birdies at the 13th, 15th and 17th gave her hope, but Feng's equally strong finish held her off.
Piller started the day level at the top of the leaderboard with Thailand's Pornanong Phatlum, who finished in third place on 13 under after a 70, and fellow American Natalie Gulbis.
Gulbis endured a nightmare final round, following two 70s and a 65 with a 10-over 82 which dropped her back to one under for the tournament and in a tie for 29th place.
She had six bogeys, two double bogeys and one birdie in a round to forget.
Germany's Sandra Gal was the highest-placed European, finishing fourth on 12 under after a 69.
Scotland's Catriona Matthew was joint 21st on four under after ending a disappointing tournament in style, going round in 66 on Sunday.