The invention provides an emulsion polymerization method for preparing a rapid vulcanization butadiene-acrylonitrile rubber. Addition of a pre-crosslinking agent increases degree of branching of a microgel in molecular structure, so as to realize low gel and high microgel content; and a vulcanization cross-linking agent added in the mid-term of a reaction, and the formed molecular structure accelerates vulcanization process in the processing of the rubber, so as to reach good vulcanization effect. As microstructure of rubber molecules is controlled and adjusted, the butadiene-acrylonitrile rubber prepared by the method provided by the invention has high microgel content and low gel content, and can easily form a stereochemical structure during a processing process; and the rubber product has good physical and mechanical properties, increased Mooney viscosity, and correspondingly enhanced tensile strength, elongation at rupture and 300% stress at definite elongation.