In　continuous-flow　reactor　(CFR),　suboptimal　hydraulic　retention　time　(HRT)　can　affect　the　substrate　loading,　anaerobic　time　and　aerobic　time　and　further　affect　the　performance　and　characteristics　of　granules,　thus　different　HRTs　(7.5,　6.0,　4.5　and　5.2　h)　were　tested　to　improve　the　phosphorus　(P)　and　carbon　(COD)　removal　of　the　continuous-flow　system　with　granules　in　this　study.　When　HRT　was　below　6.0　h,　the　COD　removal　efficiency　in　anaerobic　zone　and　the　P　removal　efficiency　in　aerobic　zone　reduced　obviously,　and　the　settling　ability　of　EBPR　granules　deteriorated.　The　residual　COD　in　anaerobic　zone　resulted　in　the　proliferation　of　filamentous　bacteria　on　the　granules　surface.　Pyrosequencing　analysis　revealed　that　Proteobacteria　was　the　dominant　phylum　in　this　system.　The　dominant　class　transformed　from　Betaproteobacteria　to　Gammaproteobacteria　when　HRT　was　reduced　from　6.0　h　to　4.5　h.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.