In this paper，the modified waterborne Polyurethane emulsion(E-WPU) was synthesized based acetone on self-emulsified process by using of Polybutylene adipate(PBA)，isophorone diisocyanate(IPDI) and dimethylol propionic acid (DMPA) as the main raw material， hydrophobic chain extension agent epoxy resin (E44)，1,4-cyclohexane dimethyl (CHDM) and isophorone ketone diamine (IPDA) as modifier．Modified and unmodified emulsion coating properties were characterized by the FT-IR，Tg,，adhesion，hardness and Tafel polarization curves．The results showed that using of E44，IPDA and CHDM had significantly improved the water resistance，hardness and adhesion on the metal of the E-WPU coating．When the mass fraction of E44，CHDM and IPDA were respectively 7%，2% and 3% in the prepolymer，and the molar ratio of the —NCO and the active hydrogen of the —OH/—NH/—NH2 group in the prepolymer (R) was 1.2，the coating had the best comprehensive performance．The water absorption rate，the hardness and the adhesion on metal surface were respectively 3.5%，HB-H and grade zero．The corrosion potential of E-WPU coating was -0.6608v，and the corrosion current density was 9.778e-7 A/cm2．