Abstract: The hydrophobically associating water-soluble copolymer (PSAM) of acryl amide with butyl styrene (BS) was synthesized by the micellar free radical copolymerization technique.GPC measurement showed that the weight average molecular weight of PSAM was 1.6868×10⁵ and environmental scanning electron microscope(ESEM) images of hydrophobically associating network-structures of PSAM in aqueous solution were obtained, indicating that the viscosification performance of PSAM was dependent on the intermolecular hydrophobic association.The study on the solution properties of PSAM showed that when the copolymer concentration was higher than 0.1 g·dl^-1, the copolymer exhibited good viscosification property, salt-thickening, temperature-thickening, pseudoplastic behavior, thixotropy and shear-thickening upon application of a low shear rate in the initial period of time.After ageing for 90 d at 80℃, the apparent viscosities of 0.2 g·dl^-1 PSAM in 0.137 mol·L^-1 NaCl solution was 53.8 mPa·s and the retention ratio of apparent viscosity was 49.2%, showing good anti-ageing property of the polymer due to the incorporation of BS into the polymer.