Abstract: In this paper,using fatty acid methyl esters of soybean oil as a raw material,the preparation of epoxidized fatty acid methyl esters in the presence of organic acid autocatalytic system was studied.The effect of organic acids,the amount of hydrogen peroxide(H₂O₂),reaction temperature,reaction time and auxiliaries(surfactants and phase transfer catalysts) on the synthesis of epoxidized fatty acid methyl esters were investigated.The epoxidation activity of organic acids was followed by formic acid> acetic acid> oxalic acid=citric acid,in which the formic acid showed the best efficiency.The addition of phase transfer catalysts(tetrabutylammonium bromide,polyethylene glycol 400) and surfactants (Tween 40,polyoxyethylene lauryl ether,cetyltrimethylammonium bromide) could reduce the epoxidation reaction in varying degrees.The results showed that the optimized epoxidation reaction parameters were as follows:fatty acid methyl esters 10 g,formic acid/H₂O₂/C=C bonds at the molar ratio of 0.6:2:1,reaction temperature of 50℃,reaction time of 6 h and no auxiliaries.Under these conditions,the epoxy value of the epoxidized fatty acid methyl esters was 5.91%.The product was characterized by ¹H-NMR and the result showed that the hydrogen absorption peaks of C=C bonds disappeared at the chemical shift of 5.4 ppm,while the hydrogen characteristic absorption peaks of epoxy bond appeared at the chemical shift of 3.0 ppm.