The　experiment　was　to　explore　the　effect　of　different　SRT　on　the　nitrogen　removal　efficiency　and　kinetic　characteristics　of　AnAOB　by　studying　the　variation　of　nitrite　removal　loads　(Nr),　nitrite　sludge　loads　(Ns)　and　kinetic　characteristics　with　gradient　decrease　of　SRT　in　a　SBR.　The　results　showed　that　with　SRT　decreasing　from　21　d　to　12　d,　Nr　decreased　from　0.590　kg/(m3•d)　to　0.493　kg/(m3•d)　while　Ns　increased　from　0.178　kg/(kg•d)　to　0.297　kg/(kg•d),　and　the　N-removal　performance　of　the　whole　system　was　reduced　but　the　N-removal　efficiency　of　unit　mass　of　AnAOB　was　significantly　improved.　The　Monod　model　can　well　simulate　the　kinetic　behavior　of　AnAOB　at　different　SRT.　The　maximum　specific　degradation　rate　(vmax)　increased　from　0.406　d-1　to　0.826　d-1　and　the　semi-saturated　constant　(Ks)　increased　from　23.3　mg/L　to　95.3　mg/L,　which　indicated　that　gradiently　decreasing　SRT　can　screen　and　purify　AnAOB　with　faster　grow　rate,　while　the　affinity　for　the　substrate　gradually　deteriorated　and　the　stability　decreased.　©　2018,　Editorial　Board　of　Journal　of　Harbin　Institute　of　Technology.　All　right　reserved.