In　order　to　investigate　the　performance　of　biological　nutrients　removal　and　denitrifying　phosphorus　removal　in　the　A2O　process　when　treating　low　C/N　ratio　domestic　wastewater,　a　reactor,　with　a　working　volume　of　52.5　L,　was　used　in　this　study.　The　volume　ratio　of　anaerobic/anoxic/aerobic　zone　was　1/1/2　and　the　major　operating　parameters　were:　HRT　8　h,　sludge　recycle　ratio(r)　70%,　aerobic(nitrate)　recycle　ratio(R)　300%.　The　results　showed　that　85.4%　of　TN　and　93.3%　of　SOP　could　be　removed　when　the　C/N　ratio　was　7.89.　There　was　denitrifying　phosphorus　removal　in　the　system.　Moreover,　up　to　25.3%　of　the　SOP　could　be　removed　in　the　anoxic　zone　by　this　way.　The　TN　removal　efficiency　was　reduced　to　62.2%　when　decreasing　the　C/N　ratio　to　4.20　with　the　same　operating　parameters.　However,　the　SOP　removal　efficiency　was　kept　over　96.0%.　The　TN　removal　efficiency　was　70.7%　and　up　to　55.2%　of　SOP　was　removed　in　the　anoxic　zone　when　changing　the　volume　ratio　of　anoxic/aerobic　to　5/8.　With　the　same　anoxic/aerobic　ratio,　when　changing　the　aerobic(nitrate)recycle　ratio　to　250%,　the　maximal　denitrifying　phosphorus　removal　could　be　achieved,　removing　77.3%　of　the　TN　from　the　system.　Enhanced　denitrifying　phosphorus　removal　in　the　A2O　process　is　an　effective　way　to　counteract　the　disadvantages　of　carbon　shortage　for　biological　nutrients　removal.