According　to　the　determining　results　of　total　phosphorus　for　the　A/A/O　all-process　of　a　wastewater　treatment　plant　of　Beijing　in　China,　it　were　analyzed　for　the　phosphorus　balance　of　the　system　and　the　denitrifying　phosphorus　removal　of　the　anoxic　phase.　And　it　was　discussed　for　the　correlation　between　the　phosphorus　removal　and　process　operating　parameters.　Then　the　optimal　parameters　of　A/A/O　process　control　were　proposed　based　on　the　phosphorus　removal.　The　main　conclusions　were　as　follows:　The　phosphorus　removal　of　anoxic　phase　and　oxic　phase　were　4.97mg/L　and　5.5mg/L　separately,　which　there　was　the　obvious　denitrifying　phosphorus　removal　in　anoxic　phase.　On　the　whole,　the　phosphorus　load　of　the　influent　and　effluent　in　the　process　was　balance,　the　total　phosphorus　removal　rate　of　sewage　was　about　7894%.　There　was　a　negative　correlation　relation　between　phosphorus　removal　rate　and　sludge　retention　time.　The　larger　excess　activated　sludge　discharge,　the　lower　phosphorus　accumulation　in　the　A/A/O　process　system.　The　appropriate　sludge　discharge　of　the　process　should　be　remained　at　40005000m3　per　day.　The　phosphorus　load　proportion　of　influent　accounted　for　98　percent　of　entering　into　the　process　system,　the　rest　came　from　the　waste　liquor　of　sludge　treatment　process　in　the　wastewater　treatment　plant.　In　the　discharge　phosphorus　load　of　the　treatment　plant,　dewatered　sludge　cake　had　taken　out　84　percent,　effluent　accounted　for　14　percent,　and　the　waste　liquor　of　sludge　treatment　process　was　only　2　percent.　©　2011　IEEE.