Hydroxypropyl acrylate-citrate (HPA-CAE) was prepared by esterification of citric acid and hydroxypropyl acrylate. Then a graft copolymer was synthesized by copolymerization of degraded starch and HPA-CAE using horseradish peroxidase (HRP) /H2O2/acetylacetone (ACAC) as catalyst. The effects of amount of HRP, H2O2, ACAC and CA-HPA on grafting efficiency (GE) and grafting percentage (GP) were investigated. The optimum graft copolymer was synthesized by graft copolymerization of 50 g degraded starch (wt 15%) with 13.9 g CA-HPA in the presence of 6.4 mg HRP/4.7 mL H2O2/1.2g ACAC. The structure of the copolymer was characterized by FTIR and NMR. The applied results showed that the retanned leather had the merits of softness, fine grain and uniform thickness.