The　sulfur-based　autotrophic　denitrification　reactor　was　set　up　and　its　denitrification　performance　was　evaluated　in　this　study.　The　denitrification　activity　of　the　sludge　was　determined　by　batch　tests,　and　the　microbial　community　structure　was　revealed　by　scanning　electron　microscopy(SEM)　and　high-throughput　sequencing.　The　influent　NO3--N　concentration　of　the　reactor　operated　with　sequencing　batch　mode　was　80mg/L.　The　autotrophic　denitrification　performance　increased　with　the　hydraulic　retention　time　(HRT)　gradually　shortened　from　12h　to　6h,　the　total　inorganic　nitrogen(TIN)　removal　efficiency　and　the　average　TIN　removal　loading　rate　of　the　reactor　during　the　stable　period　were　99.1%　and　0.158kg　N/(m³•d),　respectively.　The　maximum　NO2--N　concentration　during　the　SBR　cycle　was　13.3mg/L,　the　pH　value　decreased　from　7.38　to　6.94　during　the　reduction　process　from　NO3--N　to　NO2--N,　and　the　pH　value　remained　stable　during　the　process　of　reducing　NO2--N　to　N2.　The　batch　test　results　showed　that　the　NO3--N　removal　rate　of　sulfur　autotrophic　denitrifying　bacteria　and　heterotrophic　denitrifying　bacteria　were　0.515and　0.196kg　N/(kg　VSSd),　respectively,　and　the　NO2--N　removal　rate　of　sulfur　autotrophic　denitrifying　bacteria　was　0.117kg　N/(kg　VSSd),　the　sludge　had　both　autotrophic　denitrification　activity　and　heterotrophic　denitrification　activity.　SEM　images　showed　that　both　rod-shaped　bacteria　and　spherical　bacteria　were　observed　in　the　sludge.　The　dominant　sulfur　autotrophic　denitrifying　bacteria　in　the　sludge　were　Thiobacillus,　Sulfurimonas　and　Thermomonas,　with　relative　abundance　of　14.5%,　7.6%　and　6.0%,　respectively.　©　2020,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.