The　effects　of　influent　C/N　ratio　and　C/P　ratio　on　biological　nutrient　removal　performance　were　investigated　in　a　lab-scale　UniFed　SBR　apparatus　treating　real　domestic　wastewater.　The　results　showed　that　TN　removal　efficiency　increased　as　C/N　ratio　increased　from　43.6%　at　2.8　to　80.8%　at　5.7.　But　when　C/N　ratio　increased　further,　TN　removal　efficiency　increased　very　slowly.　This　was　because　when　C/N　ratio　was　higher　than　5.7,　complete　denitrification　in　the　sludge　blanket　during　feed/decant　period　had　been　achieved,　TN　removal　efficiency　during　this　period　always　kept　the　maximum　value　and　only　TN　removal　efficiency　during　aeration　period　rose　as　C/N　ratio　increased.　PO43-　removal　efficiency　increased　as　C/N　ratio　increased　from　27.3%　at　2.8　to　88.1%　at　5.7.　When　C/N　ratio　was　6.5　and　above,　PO(4)(3-)concentration　couldn＇t　be　detected　in　the　effluent.　When　influent　C/N　ratio　and　volumetric　exchange　ratio　were　fixed　at　6　and　33%　respectively,　as　C/P　ratio　was　higher　than　33,　PO43-　concentration　of　effluent　always　remained　below　the　detection　level　and　phosphorus　removal　efficiency　kept　stable　at　100%,　but　as　the　C/P　ratio　was　lower　than　33,　phosphorus　removal　efficiency　increased　as　C/P　ratio　increased　linearly.　C/P　ratio　hardly　affected　TN　removal　efficiency,　which　always　kept　at　82.2%-85.8%　in　this　study.