The　A/A　sequencing　batch　reactor(SBR)　was　used　to　enrich　denitrifying　and　phosphorus　accumulating　bacteria(DPB).　Denitrifying　and　phosphorus　accumulating　tests　were　performed　by　using　acetic　acid　and　glucose　as　substrate.　The　metabolic　mechanism　and　change　of　phosphorus/nitrate/COD　in　water　and　polyhydroxyalkanoates(PHA)/glycogen　in　sludge　were　studied.　The　release　of　poly-phosphate　would　control　the　combination　of　PHA.　At　the　anoxic　stage　breakdown　of　PHA　was　used　as　carbon　source　to　denitrify　nitrate,　and　the　adenosine　triphosphate(ATP)　thus　generated　provided　energy　for　accumulating　phosphorus.　So　it　is　important　to　track　the　change　of　PHA,　not　COD　when　the　denitrifying　and　phosphorus　accumulating　process　was　studied.　When　glucose　was　used　as　substrate,　fermented　bacteria　broke　down　glucose　into　volatile　organic　acid　of　small　molecules,　then　non-fermented　bacteria　could　play　a　role　fully.　At　the　anaerobic　stage,　85%　energy　came　from　the　release　of　phosphorus,　15%　energy　came　from　the　fermentation　of　glycogen.　At　the　anoxic　stage,　85%　PHA　breakdown　was　used　to　accumulate　phosphorus,　15%　was　converted　into　glycogen.　The　metabolic　mechanism　could　be　simplified.　©　All　Rights　Reserved.