The invention provides a method for synthesizing an acrylic ester-acrylonitrile emulsion copolymer. The method uses an acrylic monomer to match acrylonitrile, uses water-soluble thermolysis peroxide as an initiator, uses a mixed system of anionic emulsifier and nonionic emulsifier as emulsifier, and performs emulsion copolymerization through the prior emulsion copolymerization method to produce the acrylic ester-acrylonitrile emulsion copolymer. The method adopts a mode which adds the monomer, the emulsifier and the initiator in batches, and a high-temperature emulsion polymerization technology which controls temperature of two stages stepwisely, so the bounding quantity of the acrylonitrile and the synthesized emulsion copolymer is more than 25 percent. The emulsion copolymer has excellent oil resistance and solvent resistance, and excellent low-temperature resistance and high-temperature resistance to tolerate a low temperature down to 45 DEG C below zero and a high temperature up to 220 DEG C, and is very suitable for producing asbestos or a non-asbestos beater sheet for an automobile sealing gasket.