Chitosan-g-poly (dimethyl siloxane) (PDMS) copolymer was prepared by grafting PDMS prepolymer onto chitosan. PDMS prepolymer was prepared by ionic ring opening polymerization of octamethylcyclotrisiloxane (D-4) using n-buthyl-lithium (BuLi). The tensile strength and elongation of chitosan-g-PDMS copolymer were mostly constant regardless of PDMS prepolymer grafting %. While critical surface energy of chitosan is about 32 dyne/cm, that of chitosan-g-PDMS copolymer was a little decreased to 25 similar to 29 dyne/cm by grafting PDMS onto chitosan.