Abstract: The thermodynamics of micellization for polystyrene-b-poly(ethylene/propylene) two-block copolymer(SEP) in the mixtures of n-octane and benzene with different proportions have been studied in this paper. The critical micelle concentrations(CMC) of micelle solutions at various temperatures were measured by low angle laser light scattering photometer(LALLS). The results show that the micellization process of nonpolar copolymer SEP in hydrocarbon solvents are exothermal, and the entropy change is negative. In contrast, for ordinary surfactants in water, it is the enthalpy contribution to the energy change which is responsible for micellization.