To　investigate　the　occurrence　and　characteristics　of　denitrifying　phosphorus　removal,　a　lab-scale　A2O　reactor　with　working　volume　of　52.5　L　was　employed　to　treat　municipal　wastewater.　The　effects　of　influent　COD/TN　ratio　and　the　volume　ratio　of　anoxic　zone　to　aerobic　zone　on　denitrifying　phosphorus　removal　were　studied.　Results　show　that　36%　of　total　soluble　phosphorus　can　be　removed　in　the　anoxic　reactor　when　the　HRT　is　8　h,　sludge　recycle　ratio　is　70%　and　internal　recycle　ratio　is　250%.　Results　of　batch　experiment　show　that　more　than　35.4%　of　phosphorus　accumulating　organisms　(PAOs)　in　the　A2O　system　can　be　denitrified.　The　ratio　of　anoxic　phosphorus　uptake　increases　with　the　decrease　of　influent　COD/TN　ratio.　Denitrifying　phosphorus　removal　can　also　be　enhanced　by　increasing　the　ratio　of　anoxic　zone　to　aerobic　zone　from　1/1　to　5/8.　Meanwhile,　the　TN　removal　efficiency　is　increased　from　62%　to　70%.　It　is　a　more　energy-efficient　way　compared　with　the　increase　of　internal　recycle　ratio,　which　can　increase　the　ratio　of　anoxic　phosphorus　uptake.　Enhancing　the　denitrifying　phosphorus　removal　in　A2O　process　is　an　effective　way　to　enhance　biological　nutrient　removal　in　treating　municipal　wastewater　with　low　C/N　ratio.