Abstract: In order to eliminate the waste cooking oil harm on human health and reuse it effectively, mixed fatty acid extracted from waste cooking oil by a series of processing:saponification-salting-out rinsing-acidification-drying, reacted with M inputed at a steady rate, when the reaction temperature at 120 ℃，red phosphorus as catalyst and reaction time is 8 h. The α derived fatty acid——M-105 was obtained and applied into the reverse flotation of Jianshan magnetite. The satifactory results of a grade of 70.26%, recovery of 83.00% was obtained.

Key words: Waste cooking oil, αderivatives of fatty acids, Flotation