In　this　study,　four　sequencing　batch　reactors　(SBR),　with　the　sludge　retention　time　(SRT)　of　5,　10,　20　and　40　d,　were　used　to　treat　domestic　wastewater,　and　the　effect　of　SRT　on　nitrite　accumulation　in　the　biological　nitrogen　removal　SBR　was　investigated.　The　real-time　control　strategy　based　on　online　parameters,　such　as　pH,　dissolved　oxygen　(DO)　and　oxidation　reduction　potential　(ORP),　was　used　to　regulate　the　nitrite　accumulation　in　SBR.　The　model-based　simulation　and　experimental　results　showed　that　with　the　increase　of　SRT,　longer　time　was　needed　to　achieve　high　level　of　nitritation.　In　addition,　the　nitrite　accumulation　rate　(NAR)　was　higher　when　the　SRT　was　relatively　shorter　during　a　112-day　operation.　When　the　SRT　was　5　d,　the　system　was　unstable　with　the　mixed　liquor　suspended　solids　(MLSS)　decreased　day　after　day.　When　the　SRT　was　40　d,　the　nitrification　process　was　significantly　inhibited.　SRT　of　10　to　20　d　was　more　suitable　in　this　study.　The　real-time　control　strategy　combined　with　SRT　control　in　SBR　is　an　effective　method　for　biological　nitrogen　removal　via　nitrite　from　wastewater.