A new multifunctional mPEG-b-PAA-grafted chitosan copolymer possessing amino and carboxyl groups, mPEG-b-PAA-g-CHI (compound 6), was designed for a potential application in gene/drug delivery and synthesized by the methods of reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylic acid (AA) and grafting reaction of a biodegradable chitosan (CHI) derivative. Completion of the reactions and characterization of the resulting compounds were demonstrated by 1H NMR, FTIR and gel permeation chtomatography (GPC) studies. The results show that the molar ratio of amino groups to carboxyl groups in the copolymer (compound 6) is 0.41:0.59.