In　order　to　study　the　effects　of　aging　on　rheological　and　molecular　properties　of　styrene-butadiene-styrene　(SBS)　modified　asphalt,　rheological　and　gel　permeation　chromatography　(GPC)　experiments　were　conducted　on　unaged　and　aged　asphalt　binders.　The　results　show　that　the　penetration　of　SBS　modified　asphalt　droped　with　aging.　The　softening　point　of　SBS　modified　as-phalt　rises　with　the　aging　progress.　The　molecular　oxidative　condensation　effect　exceeds　the　down　regulation　effect　of　SBS　degradation,　leading　to　an　increasing　viscosity.　After　aging,　ductility　at　5　degrees　C　sharply　attenuates　and　asphalt　shows　brittleness　and　no　longer　meets　the　requirements　for　high-grade　highway　pavement.　SBS　decomposition　can　inhibit　the　aging　effect　of　asphalt　molecules.　This　can　restrain　strengthening　of　high-temperature　performance　and　reduction　of　low　temperature　anti-crack　property　of　SBS　modified　asphalt.