Rumford followed last week's playoff win at the Ballantine's Championship in South Korea with a fourth-stroke win in China for his fifth European Tour title. He is the 31st player to win back-to-back events on the tour and the first since Branden Grace early last year.
Rumford built on his one-stroke, third-round lead with six birdies over his first 14 holes Sunday and coasted in to a 4-under-par 68 and 72-hole total of 16-under 272.
Rumford led Ilonen by one after Ilonen had birdies at Nos. 10 and 11 but the tournament turned on the next three holes. Rumford started a string of three consecutive birdies at 12 -- a sharp chip shot setting up the first birdie and a 45-foot putt creating the second -- while Ilonen had bogeys at 14 and 15 for a five-stroke swing.