The　practical　application　of　anaerobic　ammonia　oxidation　(anammox)　process　is　hindered　because　of　its　strict　demand　of　an　anaerobic　environment.　Due　to　the　slow　growth　cycle　of　anammox　bacteria　and　the　high　cost　of　wastewater　deoxidation,　it　is　difficult　to　improve　the　contribution　rate　of　denitrification　in　anammox　pathway.　Sulfur　oxidizing　bacteria　(SOB)　consume　oxygen　in　the　process　of　oxidizing　sulfur　elements　to　provide　a　better　anaerobic　environment　for　anammox　bacteria,　and　sulfur　autotrophic　denitrification　can　also　remove　nitrate　produced　during　the　anammox　process　for　deep　nitrogen　removal.　The　analysis　of　cell　hydrophobicity　and　EPS　secondary　structure　were　consistent,　which　showed　that　the　biofilm　of　A-SAD　(anammox-　sulfur　autotrophic　denitrification)　system　exhibited　stronger　adhesion　and　a　more　stable　structure.　The　functional　genes　of　ammonia　oxidation　(amoA)　and　nitrite　oxidation　(nxrA)　were　reduced　by　more　than　90　%,　implying　that　SAD　provided　a　favorable　anaerobic　environment　for　anammox　and　reduced　the　cost　of　deoxidation　in　actual　operation.　The　relative　abundance　of　Candidatus_Kuenenia　increased　nearly　threefold,　becoming　the　dominant　anammox　bacteria　in　low　substrate　environment,　while　other　anammox　bacteria　almost　disappeared.　The　increase　of　the　relative　abundance　of　Thiobacillus　and　Desulfovibrio　were　beneficial　to　the　transformation　of　S0　into　bio-sulfur　(Bio-S0)　through　redox,　which　provided　the　possibility　for　the　recovery　and　utilization　of　sulfur.　This　experiment　provides　a　comprehensive　understanding　of　the　nitrogen　and　sulfur　conversion　mechanism　for　the　deoxidation　and　sulfur　recovery　of　anammox　in　practical　applications.　©　2023　Elsevier　Ltd