The synthesis, alcoholysis and aminolysis of α-methyl methacrylate ester - maleic anhydrid - vinyl acetate (AMV) was described and characterized in this work. The solidifying point (SP) and cold filter plugging point (CFPP) depression effects of the AMV terpolymer and its alcoholvsis and aminolysis products were determined, and the terpolymers were charactered by IR. The AMV terpolymer was synthesized at the molar ratio (4: 1: 2) of α-methyl methacrylate ester, maleic anhydride, vinyl acetate with 1.2% initiator at 85℃ for 5 hours. With 0.1% additive dosage , the AMV terpolymer can reduce the SP and CFPP of three kinds of diesel oils (obtained from PetroChina Lanzhou Petrochemical Company) by 10℃, 16℃ ,11℃ and 1℃ ,3℃ ,2℃, respectively. The alcoholysis and aminolysis of the AMV polymer were also carried out. With 0.1% additive dosage, the aminolysis products through octadecylamine could reduce the SP and CFPP of diesel oils by 10℃, 14℃ ,9℃ and 2℃ ,5℃ ,3℃, respectively.