The invention discloses poly-vinyl versatate-vinyl acetate-ethylene emulsion and an emulsion polymerization preparation method. The poly-vinyl versatate-vinyl acetate-ethylene emulsion is copolymer emulsion with the solid content of 55.0-57.0 percent, which is prepared via free radical emulsion polymerization with vinyl versatate, vinyl acetate and ethylene as monomers, compound polyvinyl alcoholas protective colloid, octylphenol polyoxyethylene ether as an emulsifier and with the presence of redox initiators. The weight-average molecular weight of the terpolymer emulsion is 122,984-130,000,and the molecular weight distribution width is 5.295-6.000. The film prepared with the copolymer emulsion has good weathering resistance, alkali resistance, hydrolysis resistance, uniform particle size, appropriate molecular weight and distribution, low glass transition temperature (T is equal to below 2 DEG C), good film-forming performance, excellent performance and wide scope of application.