A　lab-scale　A2O　process　was　operated　to　investigate　the　performance　of　biological　nutrients　removal　and　denitrifying　phosphorus　removal　from　low　ρ(C)/ρ(N)　ratio　domestic　wastewater.　The　results　showed　that　only　about　47.1%　of　TN　could　be　removed　with　effluent　ρ(NO3--N)　above　35　mg/L　when　the　A2O　process　was　operated　without　the　pre-anoxic　zone　and　additional　carbon　source.　Under　this　condition,　both　conventional　and　denitrifying　phosphate　removal　was　not　observed　in　the　anoxic　zone.　When　the　A2O　process　was　operated　with　the　pre-anoxic　zone,　about　60.7%　of　TN　and　55.9%　of　PO43--P　could　be　removed.　Moreover,　denitrifying　phosphate　removal　occurred　with　a　removal　efficiency　of　31.4%-46.9%　in　the　anoxic　zone.　After　the　ρ(C)/ρ(N)　ratios　were　increased　by　adding　the　carbon　sources,　biological　nutrients　removal　was　enhanced　with　the　TN　removal　of　74.4%　and　the　ρ(PO43--P)　in　the　effluent　below　0.5　mg/L,　and　the　denitrifying　phosphate　removal　efficiency　was　up　to　66.2%-90.9%.　Furthermore,　the　variations　of　PHA　and　glycogen　were　investigated.　The　relative　metabolic　activity　of　the　DNPAO　(denitrifying　phosphate　accumulating　organism)　increased　from　31.1%　in　the　seed　sludge　to　74.7%　in　the　acclimated　sludge.　The　carbon　sources　utilization　efficiency　is　upgraded　with　the　achievement　in　denitrifying　phosphate　removal　in　the　A2O　process.