HHydroxyethyl methylacrylate (HEMA) was grafted onto the degraded starch by grafting copolymerization using ammonium persulfate (APS) as initiator. The effect of temperature, weight fraction of APS and HEMA, reacting time on the grafting efficiency (GE) and grafting percentage (GP) were investigated. The grafting starch with 40 % GE and 27.5 % GP was obtained when w（ST）=16.4 %,w（HEMA）=5.08 %, w（APS）= 0.84 % and reacted at 50 ℃ for 5 h. The structure and properties of the grafting starch were characterized by FTIR and GPC. Applying of the grafting starch in the process of retanning endow the retanned leather an excellent increment in thickness. The leather retanned by this grafting starch with different GE and GP got the increasing properties of plump, soft, good elasticity and strong foaming feels in addition to increase in the GE and GP.