Aerobic　synthesis　of　poly-β-hydroxybuyrate　and　uptake　of　phosphorus　in　anaerobic/aerobic　condition　were　observed　in　a　sequencing　batch　reactor　(SBR)　with　real　domestic　wastewater.　The　results　show　that　with　easily　degradable　organic　substrate,　the　uptake　of　ortho-phosphate　and　the　synthesis　of　PHAs　happens　insimultaneously,　which　is　consistent　with　traditional　theory.　The　rate　of　PHAs　synthesized　in　aerobic　condition　(ηO)　is　largely　higher　than　the　rate　of　PHAs　synthesized　in　anaerobic　condition　(ηAn).　And　the　former　is　about　five　times　larger　than　the　later.　Anaerobic/aerobic　condition　can　enrich　the　populations　of　the　PAOs,　and　restrains　the　growth　of　the　OHOs,　availably.　ORP　profile　should　be　considered　as　the　key　characteristic　point　of　phosphorus-uptake　in　the　enhanced　bio-logical　phosphate　removal　system.