The　characteristics　of　biological　nitrogen　(N)　and　phosphorus　(P)　removal　under　different　nitrate　recycling　ratios　were　investigated　in　a　Anaerobic/Anoxic/Oxic　(A2O)-Biological　Contact　Oxidation　(BCO)　system　when　treating　low　C/N　in　municipal　wastewater.　The　results　indicated　that　the　removal　of　N　and　P　was　achieved　simultaneously,　and　denitrifying　phosphorus　removal　(DPR)　process　was　realized　with　the　total　hydraulic　retention　time　(HRT)　of　A2O　at　8h,　sludge　reflux　ratio　of　100%,　and　nitrate　recycling　ratios　set　as　100%,　200%,　300%　and　400%　respectively.　The　effluent　concentration　of　COD　was　less　than　50mg/L.　The　removal　efficiencies　of　total　nitrogen　(TN)　were　48.8%,　66.5%,　75.6%　and　62.5%,　and　the　removal　efficiencies　of　total　phosphorus　(TP)　were　86.0%,　90.3%,　91.0%　and　95.0%　under　various　nitrate　recycling　ratios.　When　the　nitrate　recycling　ratio　was　set　at　300%,　average　concentration　of　TN　and　TP　in　effluent　were　14.96mg/L　and　0.49mg/L.　The　amount　of　denitrifying　phosphorus　removed　was　increased　slightly　as　the　nitrate　recycling　ratio　improved.　When　the　nitrate　recycling　ratio　was　set　at　400%,　the　amount　of　P　removed　by　DPR　accounted　for　98%　of　the　total　phosphorus　removed.　©,　2014,　Chinese　Society　for　Environmental　Sciences.　All　right　reserved.