A small molecule chain extender of N-(2-pyrrolidone ethyl) diethanolamine(DVP) diol was synthesized from diethanolamine(DEA) and vinylpyrrolidone(NVP).The waterborne polyurethane with different content of DVP was synthesized by DVP, polyether polyol(N220), isophorone diisocyanate(IPDI), 2,2-dimethylol-propionic acid(DMPA) and diethylene glycol (DEG). The structure of DVP was characterized by Fourier transform infrared spectroscopy (FT-IR)and nuclear magnetic resonance spectroscopy. The structure and properties of waterborne polyurethane with different content of DVP were characterized by infrared, particle size test, thermogravimetry(TGA), mechanical properties test and water absorption test. The results indicate that when the content of DVP is 0.5%(wt), emulsion particle size is 44 nm, the synthesized film has the best comprehensive performance, the tensile strength is 21.04 MPa,the maximum elongation at break is 854.6%, T5% and T50% are 269.6 and 343.5℃ respectively, water absorption is 13.41%, and the mechanical properties, heat resistance and water resistance are improved significantly compared with unmodified waterborne polyurethane.