The　selection　and　dominance　of　denitrifying　phosphorus　removing　bacteria　(DPB),　which　was　capable　of　utilizing　nitrate　as　electron　acceptor,　was　investigated　in　a　laboratory-scale　sequencing　batch　moving-bed　biofilm　reactor　(MBBR).　The　experimental　results　demonstrated　that　the　proportion　of　DPB　increased　approximately　from　11.77%　to　66.07%　of　total　phosphate　accumulating　organisms　(PAOs)　after　three　stages　selection　and　dominance.　In　the　end　of　the　third　cultivating　period,　average　removal　efficiencies　of　COD　and　TP　were　68.78%　and　69.02%,　respectively,　and　a　large　quantity　of　nitrate,　23.91　mg/L,　was　removed　in　anoxic　phase.　It　was　found　that　a　great　deal　of　PHB　about　PAOs　emerged　in　anaerobic　phase,　whereas　a　mass　of　Poly-p　about　PAOs　arose　in　anoxic　phase　by　biofilm　dyeing　method,　so　they　could　be　taken　as　evidences　to　judge　the　process　and　efficiency　of　biological　phosphorus　removal.