The　simultaneous　chemical　phosphorus　removal　(SCPR)　process　has　been　widely　applied　in　wastewater　treatment　plants　(WWTPs)　due　to　the　high　phosphorus　removal　efficiency　through　the　synergy　of　biological　and　chemical　phosphorus　removal　(BPR　and　CPR).　However,　phosphorus　removal　reagents　could　affect　the　bacterial　community　structure　in　the　SCPR　system　and　further　affect　the　BPR　process.　The　BPR　phenotypes　and　community　structures　in　the　SCPR　system,　especially　the　population　of　polyphosphate-accumulating　organisms　(PAOs),　are　not　completely　clear.　In　order　to　clarify　these　problems,　the　phosphorus　removal　performance　and　the　PAO　population　in　a　full-scale　SCPR　system　were　investigated.　Results　showed　that　diverse　PAOs　still　existed　in　the　SCPR　system　though　the　BPR　phenotypes　were　not　observed.　However,　the　relative　abundances　of　Accumulibacter　andTetrasphaera,　the　two　most　important　genera　of　PAOs,　were　only　0.59%　and　0.20%,　respectively,　while　the　relative　abundances　of　Competibacter　andDefluviicoccus,　two　genera　of　glycogen-accumulating　organisms　(GAOs),　were　as　high　as　5.77%　and　1.28%,　respectively.　Batch　tests　showed　that　PAOs　in　the　SCPR　system　still　had　a　certain　polyphosphate　accumulating　metabolic　activity,　which　could　gradually　recover　after　stopping　the　addition　of　chemical　reagents.　This　study　provided　a　microbiological　basis　for　the　SCPR　system　to　recover　the　enhanced　biological　phosphorus　removal　(EBPR)　performance　under　suitable　conditions,　which　could　reduce　the　dosage　of　chemical　reagents　and　the　operational　cost.