Crosslinker　and　plasticizer　were　used　to　prepare　Styrene-butadiene-styrene　(SBS)　compound-modified　asphalt.　The　physical　and　rheological　properties　of　modified　asphalt　were　tested,　and　the　morphology　observation　and　thermal　analysis　were　used　to　study　the　structural　characteristics　of　modified　asphalt　further.　The　physical　tests　showed　that　plasticizer　(dioctyl　phthalate)　improved　the　low-temperature　properties　of　SBS-modified　(SM)　asphalt　and　crosslinker　(sulphur)　improved　the　stability　and　elastic　recovery　of　SBS/plasticizer-modified　(SPM)　asphalt.　The　SBS/plasticizer/crosslinker-modified　(SPCM)　asphalt　owns　better　physical　properties　before　and　after　ageing.　The　rheological　properties　were　studied　by　using　creep　tests.　Creep　tests　indicated　that　plasticizer　declined　the　deformation　resistance　of　SM　asphalt　and　crosslinker　increased　the　recoverable　deformation　of　SPM　asphalt.　Morphology　observation　showed　that　crosslinker　improved　the　compatibility　between　SBS　and　asphalt　greatly　and　ageing　prompted　the　degradation　of　SBS　to　a　great　extent.　Thermal　analysis　showed　the　effect　of　plasticizer　and　crosslinker　on　the　thermal　behaviour　of　SM　asphalt,　and　the　calculation　for　Ea　and　endothermic　peak　area　showed　the　structural　characteristics　of　modified　asphalt　before　and　after　ageing.