The　study　was　based　on　the　removal　of　nitrate　and　sulfide,　and　aimed　to　nitrite　accumulation.　The　process　of　autotrophic　denitrification　driven　by　sulfide　as　an　electron　donor　was　investigated　in　a　sequencing　batch　reactor.　The　research　showed　that　autotrophic　denitrification　successfully　started　on　day　22,　and　the　removal　rates　of　NO3-N　and　S2--S　were　95.8%　and　100%,　respectively,　when　the　S/N　molar　ratio　was　1.45.　When　the　S/N　ratio　was　reduced　to　0.94,　the　phenomenon　of　NO2--N　accumulation　was　observed.　NO2--N　continuously　accumulated,　and　the　maximum　accumulation　rate　was　55.3%　when　the　S/N　ratio　was　0.8.　In　the　batch　test,　the　study　showed　that　NO2--N　accumulation　was　optimal　when　the　S/N　ratio　was　0.8,　and　the　NO2--N　concentration　increased　with　increasing　NO3--N　concentration　at　the　same　S/N　ratio.　Microbial　communities　also　changed　based　on　the　high-throughput　analysis,　and　Proteobacteria　(59.5%-84%)　was　the　main　phylum.　Arenimonas　(11.4%-28.2%)　and　uncultured_f_　Chromatiaceae　(5.7%-27.5%)　were　the　dominant　bacteria,　which　complete　denitrification　and　desulfurization　throughout　the　operating　system.　Therefore,　this　study　provided　a　theoretical　basis　for　the　simultaneous　removal　of　NO3--N　and　S-2(-)-S,　as　well　as　the　accumulation　of　nitrite,　and　provided　material　support　for　anaerobic　ammonia　oxidation　technology.　(C)　2021　Elsevier　Ltd.　All　rights　reserved.