Polyphosphoric　acid　(PPA)　was　used　to　improve　the　performances　of　styrene–butadienestyrene　(SBS)　modified　(SM)　asphalt　mixture　further　and　decline　the　SBS　content,　however　the　negative　effect　of　PPA　on　the　performances　of　SM　asphalt　mixture　is　still　unclear.　The　major　purpose　of　this　paper　is　to　indicate　the　negative　effect　and　provide　an　efficient　way　to　solve　the　problem.　In　this　paper,　SM　asphalt,　SBS/PPA-modified　asphalt　(SPMA),　SBS/PPA/sulfur-modified　asphalt　(SPSMA)　were　prepared,　the　physical　properties　were　studied　and　the　morphology　was　investigated　by　using　scanning　electron　microscope　(SEM).　The　mixtures　of　base　asphalt　(BA),　SM　asphalt,　SPMA,　SPSMA　were　designed　and　prepared　in　the　light　of　Superpave　mixing　design　method　and　Phoenix　specifications.　Universal　testing　machine　(UTM)　system　was　used　to　investigate　the　effect　of　SBS,　PPA,　sulfur　on　the　properties　of　BA　mixture.　It　was　found　that　PPA　declined　the　crack,　fatigue　resistance　and　moisture　susceptibility　of　SM　asphalt　mixture　and　the　problem　can　be　solved　well　by　vulcanization,　the　morphology　change　of　SBS　from　coarse　particle　to　threadlike　one　after　vulcanization　prompted　the　swelling　of　SBS　in　asphalt.　Therefore　SBS　compound　modified　asphalt　pavement　material　with　better　performances　and　lower　cost　can　be　prepared　by　taking　advantage　of　acidification　and　vulcanization.　©　2021　Elsevier　Ltd