Styrene-butadiene-styrene　block　copolymer　(SBS)-and　styrene-butadiene　rubber　(SBR)-compound　modified　asphalts　with　good　storage　stability　and　high-　or　low-temperature　properties　before　and　after　short-　and　long-term　ageing　are　prepared　by　the　addition　of　polyphosphoric　acid　or　sulfur　selectively.　The　effect　of　PPA　and　sulfur　on　the　storage　stability,　the　physical　and　rheological　properties　of　SBS-　and　SBR-modified　asphalts　before　and　after　ageing　is　studied.　To　improve　the　storage　stability,　high-　or　low-temperature　properties　of　SBS-　and　SBR-modified　asphalts　before　and　after　ageing,　the　SBR-modified　asphalt　should　be　modified　further　only　by　the　addition　of　PPA,　the　linelike　SBS-modified　asphalt　should　be　improved　by　the　addition　of　PPA　and　sulfur,　the　starlike　SBS-modified　asphalt　should　be　improved　only.　by　the　addition　of　sulfur.　The　modification　mechanism　of　PPA　and　sulfur　in　the　preparation　of　those　polymer　modified　asphalts　(PMAs)　is　studied　further.　(C)　2013　Elsevier　Ltd.　All　rights　reserved.