Thermo-responsive chitosan-g-poly (N-isopropylacrylamide), composing a chitosan backbone with thermoassociative poly(N-isopropylacrylamide) side chains, was synthesized by copolymerization of low MW chitosan and (N-isopropylacrylamide) at different feeding mole ratios (1:1, 1:2, 1:3, and 1:4). The graft copolymers low MW chitosan, and poly(N-isopropylacrylamide) were characterized by FTIR, NMR, thermogravimetric analysis, and solubility test. The grafting compositions of the copylymers were roughly estimated to be 1:0.7, 1:1.3, 1:2.5, and 1:2.8. The obtained copolymer exhibited both pH- and thermo-responsive behaviors. It dissolved in water at pH 3-8 at room temperature, and became cloudy when temperature was increased. This results from pH-sensitive chitosan and thermo-responsive poly(N-isopropylacrylamide) graft chains in the copolymers. The association temperatures of the copolymers in water secreased slightly as the copolymer concentration and PHIPAAm side chains increased.