In　this　study,　three　concentrations　of　Na2SO3　solution　were　used　to　remove　dissolved　oxygen　in　the　influent　water　and　enter　the　up-flow　anaerobic　sludge　bed　reactor　(UASB).　This　study　investigated　the　effects　of　three　concentrations　of　Na2SO3　on　the　inhibition　and　performance　recovery　of　the　ANAMMOX　system　and　the　structure　of　the　microbial　community.　The　results　showed　that　although　Na2SO3　had　a　deoxidizing　function,　the　ANAMMOX　system　underwent　a　sulfate　reduction　reaction　after　adding　Na2SO3,　and　the　reduction　product　was　mainly　H2S,　which　caused　the　AnAOB　to　be　inhibited　by　sulfide.　The　denitrification　performance　was　less　than　1/2　of　that　under　normal　conditions.　The　ANAMMOX　system　was　restored　by　immediately　removing　Na2SO3　and　reducing　nitrogen　load.　After　11,　20,　and　34　days,　the　performance　of　the　ANAMMOX　system　returned　to　normal,　but　low　concentrations(45　mg/L)　required　a　long　recovery　time.　High-throughput　sequencing　analysis　showed　that　the　community　of　the　ANAMMOX　system　changed　significantly.　Before　and　after　the　experiment,　the　relative　abundance　of　ANAMMOX　functional　bacteria　Candidatus　Brocadia　decreased　from　32.66%　to　21.4%,　and　Candidatus　Kuenenia　decreased　from　7.3%　to　4.06%.　However,　the　relative　abundances　of　Armatimonadetes　and　Ignavibacteriae　increased　from　below　2%　to　about　20%.　At　the　same　time,　Thiobacillus　and　Desulfuromonadales　were　observed.　This　paper　explores　and　summarizes　the　cause　of　Na2SO3＇s　inhibition　of　AnAOB,　highlights　the　recovery　of　AnAOB　after　inhibition　for　the　stable　operation　and　deepens　the　understanding　of　the　environmental　conditions　regulating　the　ANAMMOX　process.　　©　2022　Elsevier　Ltd.