Abstract: The synthesis technology of epoxy fatty acid methylesters was studied. By gas-chromatography and chemical analysis, the best condition of the synthesis technology was obtained as follows: fatty acid methylester 100g, phosphoric acid 0.6mL, formic acid 9mL, petroleum ether 50mL,reaction temperature 65℃, reaction time 3.5 h. The properties of epoxy fatty acid methylesters were as follow: epoxy value 4.89%, acid value 0.2mg/g,iodine value 9-10g/100g, viscosity 5.87mm2/s. Through the test on pour-point depressing properties of biodiesel by adding epoxy fatty acid methylester, it was found that the epoxy product could reduce cold filtering point of biodiesel 3℃,but had no effect on freezing point.