The copolymers of N-isopropylacrylamide(NIPAM) and cholesteryl acrylate (CHA) in different molar ratios were synthesized and characterized．The surface activity and micellar behavior of the copolymers in aqueous solution were studied by surface tension method and fluorescence probe method．The Lower Critical Solution Temperature (LCST) of the copolymers was determined by fluorescence probe and turbidity measurement method Results showed that the incorporation of hydrophobic comonomer CHA led to a lower LCST than PNIPAM and the LCST decreased with the increase of the ratio of CHA．The copolymers in aqueous solution had obvious aggregation behavior with the increase of their concentrations It was evident that the introduction of a small amount of CHA units into the polymer backbone could lead to a very dramatic effect on the amphiphilic properties of the copolymers．The inner core of the micelles formed by self-aggregates of CHA segments of the copolymers was observed to encapsulate hydrophobic compounds

such as cholesterol(a drug model)．With the increase of cholesterol amount in the sample solutions with the same polymeric concentrations

the average size of the formed micelles shifted to a larger value

which indicated that more cholesteml molecules were encapsulated in the micelles．