The micellization of thermo-responsive dextran-g-PNIPAM copdymem in aqueous solutions was studied by means of surface tension technique．The surface tension of the aqueous solutions of the graft copolymers was determined overthe concentration range of 0.0001 wt％ to 0.5 wt％ at two temperatures(15 and 37℃)．It was found that the absorption of the grit polyrners at the air/water interface behaved in a dynamic way．The critical micellization concentration (CMC) of the eopolymers was determined from euives of the surface tension versus lg concentration The micellization behavior depended closely on the grafting of the copolymers and the aqueous solution temperature．Micelles could be formed in the lower concentrations when increasing PNIPAM contents of the copolymers or raising the aqueous solution temperature More importantly

the eopolymers showed CMCs in all cases no mater whether the temperature was hisher than the phase transition temperature(LCST) of the eopolymere or not．An explanation was given for understanding the phenomenon.