Chitosan-graft-poly(L-glutamic acid)(CS-g-PGA) copolymer was successfully synthesized by grafting polymerization of γ-benzyl-L-glutamate N-carboxyanhydride onto the modified chitosan chains.The self-assembly behavior of such a CS-g-PGA amphiphilic copolymer was studied.The results show that spherical nanoparticles have been formed.The size of CS-g-PGA nanoparticles is found to be controlled by the grafting ratio of PGA.These bio-based polysaccharide/polypeptide hybrid nanoparticles with controllable size may have great potential application in biomedical fields,such as drug delivery systems.