Three　sequencing　batch　reactors　(SBRs)　with　different　concentrations　of　graphene　oxide　(GO.　0.1　and　10mg/L)　were　established　to　clarify　the　intrinsic　mechanism　of　GO　deteriorating　the　nitrogen　removal　performance　of　activated　sludge　(AS).　The　results　showed　that　1mg/L　GO　had　no　significant　inhibitory　effect　on　the　performance　of　AS.　10mg/L　GO　reduced　the　total　nitrogen　(TN)　removal　efficiency　of　AS　by　17.63%.　Moreover.　GO　exposure　increased　the　oxidative　stress　levels　in　AS　by　198.51%　and　307.13%.　respectively.　The　microorganisms　responded　to　the　GO　stress　by　secreting　more　extracellular　polymers　(EPS).　16S　rRNA　gene　sequencing　showed　that　GO　significantly　affected　the　abundance　of　genera　with　nitrogen　removal　function.　The　abundance　of　common　genera　responsible　for　nitrification　(Nitrosomonas　and　Nitrospira)　and　denitrification　(Candidatus_Accumulibacter.　and　Thauera.　etc.)　decreased　with　increasing　GO　concentration.　Functional　gene　prediction　showed　that　GO　reduced　the　abundance　of　genes　related　to　nitrogen　removal.　The　abundance　of　genes　related　to　NH4+-N　oxidation　(amoA.　amoB.　amoC)　and　NO2--N　reduction　(nirK.　nirS)　decreased　significantly　with　the　accumulation　of　GO.　In　this　study.　the　intrinsic　mechanism　of　effect　on　nitrogen　removal　performance　by　GO　was　deeply　analyzed　from　the　perspective　of　functional　genes.　©　2024　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.