Chitosan (CS) is a well-known natural polysaccharide with good biocom-pa tibility and biodegradability. Graft copolymerization of poly (methyl vinyl ketone) (PMVK) onto chitosan was conducted by free radical method using KPS or CAN as an initiator. Nanoporous microspheres were, synthesized by, water-in-oil (W/O) emulsion method with glutaraldehyde(GA) as a closslinker, Tween80 (R) as a emulsifier, followed by UV irradiation to confer nanopores by photodegradation of PMVK. Graft copolymers were characterized by FT-IR and NMR spectroscopies, and their grafting percentages were calculated by weight percentage residue of TGA thermograms. FE-SEM showed CS-g-PMVK microspheres were approximately 5 mu m in diameter with rough surface due to photodegradation of PMVK by UV irradiation.