The isophorone diisocyanate , polytetra hydrofuran, 1, 4—butanediol, dimethylolpropionic acid were used as raw materials, and the waterborne polyurethane emulsion modified by collagen was synthesized by a prepolymer process. The collagen extracted from waste leather as a modifier was added during the process of synthesis, and the effect of collagen dosage on the emulsion and film was studied systematically and the structure of polyurethane film was characterized by FTIR, XRD and AFM. The results showed that the collagen was grafted on the main chain of polyurethane. The particle size of polyurethane emulsion and the crystallization trend of polyurethane film increased as the addition of collagen, while the surface roughness of film decreased. The optimal dosage of collagen was 10 % of the total quality of IPDI and PTMG, and the mechanical properties and water resistance of polyurethane film were optimal. The tensile index of film was 10.20 Mpa, 11.61 % higher than that of blank sample. The water absorption of film was 2.25 %, reduced by 87.82 % than the blank sample.