Abstract: In order to improve the flotation performance of fatty acid agents, the modification of cotton oleic acid with lactic acid was carried out, and the optimum conditions for synthetic agents were determined by flotation. And then the synthetic agents were characterized by infrared spectrum, the esterification rate was determined and the comparison test of flotation performance of several industrial chemicals. The results show that the optimum reaction conditions are:the mass ratio of cotton oleic acid to lactic acid is 10:3, the reaction temperature is 120℃, and the reaction time is 120 min; The infrared spectrum shows that he functional group contains hydroxyl group, carboxyl group and ester group, which indicated that the esterification reaction between cottonseed acid and lactic acid is carried out, and the esterification rate is 39.98%; Synthetic agent has better selectivity and collecting ability for mid-low grade collophane. Under the parameters of the flotation temperature of 20℃, and the dosage of 0.9 kg/t, the grade of P₂O₅ was eventually improved from 21.56% to 24.89% with the recovery of 80.39% and the mineral processing efficiency of 10.56% after normal flotation.and the indexes are far superior to those of the other four industrial agents and the raw cotton oil acid soap. It has no toxicity, no pollution, simple synthetic process, low dosage of insecticides, excellent flotation index and thus has a good application prospect.