The worldwide PMA pavement is steadily increasing. Unlike straight asphalt at the specified temperature of the performance grade, PMA has little increase in complex modulus after RFTO. Even after satisfying the complex modulus of the original binder, the complex modulus after the RTFO does not satisfy the grade, so that the SBS may be over-prescribed. Unlike straight asphalt, PMA investigated the reason that the complex modulus did not increase after RTFO in this study. SBS consists of a styrene domain and a butadiene matrix. The morphology of SBS in PMA is not clear. The PMA was heat - treated to induce the formation of styrene domain and PG evaluation was carried out. As a result, we confirmed that the formation of styrene domain with aging effect changed the complex modulus after RTFO.