Chitosan-g-PCL-b-MPEG copolymers of various compositions were successful synthesized via a protectiongraft-deprotection procedure, by the esterification of phthaloyl-protected chitosan (PHCS) with MPEG-b-PCL-COOH, which was synthesized from MPEG and e-caprolactone and carboxylated by maleic anhydride. The chemical structure of the chitosan-g-PCL-b-MPEG was characterized by Fourier transform infrared and NMR spectroscopy. The chitosan-g-PCL-b-MPEG was obtained as amphoteric hybrid with amino polysaccharide backbone and amphiphilic MPEG-b-PCL side chain. Their crystallinity and aggregation behavior in aqueous solution were also investigated.