A　novel　A2N2　system　was　developed　to　deal　with　low　C/N　domestic　wastewater.　The　operating　performance　under　different　nitrification　duration　distribution　ratio　in　N-SBR　unit　was　investigated.　The　experiment　was　conducted　as　follows:　under　the　condition　of　A2/O-SBR　unit　anaerobic　was　set　as　1.5　h,　anoxic　2　h,　aerobic　0.5　h　and　the　aeration　flow　rate　of　A2/O-SBR　and　N-SBR　units　was　100　and　120　Lh-1,　respectively,　and　then　the　nitrification　time　distribution　ratios　were　set　as　5:1,　4:1,　3.5:1,　3:1,　7:1　and　8:1　to　determine　the　optimal　operation　parameter.　The　results　indicated　that　the　efficient　utilization　of　carbon　sources　was　achieved　in　the　A2/O-SBR　unit,　while　the　nitrification　duration　distribution　ratio　had　little　impact　on　the　removal　of　organic　substances.　In　order　to　ensure　a　better　nitrification　and　denitrification　and　phosphorus　removal　performance,　the　first　nitrification　duration　time　must　be　≥3.5　h.　Under　the　condition　of　total　nitrification　time　was　unchanged,　an　appropriate　increase　in　the　first　nitrification　time　would　greatly　improve　the　system　TN　removal.　An　appropriate　increase　in　the　secondary　nitrification　time　can　reduce　the　effluent　NH4+　concentration　to　meet　the　first　A　discharge　standard　in　China　(GB　18918-2002).　When　nitrification　time　allocation　ratio　was　4:1,　the　system　achieved　the　optimal　nitrogen　and　phosphorus　removal　performance　with　average　effluent　concentrations　of　TN　and　PO43-　of　11.5　and　0　mgL-1,　respectively,　and　the　corresponding　average　removal　efficiency　was　75%　and　100%,　respectively.　©　All　Right　Reserved.