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 1 H 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. 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. Complex of the reactions and characterization of the resulting compounds were demonstrated by 1 H NMR, FTIR and gel permeation chtomatography GPC) studies. These results show that the molar ratio of amino groups to carboxyl groups in the copolymer (compound 6) is 0.41-0.59.