The effects of high doses (0~2.0 MGy) of gamma irradiation, at room temperature and in the presence of air, on the mechanical, electrical and thermal behavior of styrene-ethylene-butadiene-styrene/polystyrene (SEBS/PS) blends (100/0~50/50) has been studied. From the obtained results, it has been indicated that the gamma irradiation stability of SEBS was enhanced by blending with PS. After the irradiation treatment, the tensile strength, volume resistivity of blends decreased and the dielectric dissipation factor of blends increased as the absorbed dose increased. Thermal analysis data show that the introduction of PS improved the thermal property of the blends. The decrease of polyolefin content with addition of PS in the blends made the elongation at break of blends decrease intensively with the increasing of absorbed dose, especially at high doses.