A　bench-scale　nitrogen　and　phosphorus　removal　membrane　bioreactor　(UCT-MBR)　was　operated　to　treat　municipal　wastewater　in　southern　parts　of　Hebei　province　regarding　on　the　influence　of　sludge　retention　time　on　the　denitrifying　dephosphatation　propensity　and　membrane　fouling　behavior.　Either　shorter　(15d)　or　longer　(40d)　SRT　could　deteriorate　the　accumulations　of　DPAOs;　denitrifying　dephosphatation　was　strengthened　to　the　maximum　degree　under　SRT　of　25d,　the　ratio　of　the　DPAOs　to　PAOs　and　anoxic　dephosphatation　efficiency　reaching　the　maximum　values　of　50.8%　and　88%,　with　TP,TN　maximum　removal　efficiencies　of　91.7%,　73.6%　and　effluents　of　0.48,　13.3mg/L　respectively.　SRT　had　slight　effects　on　the　COD　and　ammonia　removals,　with　average　removal　efficiencies　of　88.9%,　99.7%　and　effluents　of　30.8,　0.15mg/L　respectively;　with　the　prolonged　SRT,　the　increase　of　MLSS　concentration,　the　SMP　＜　1kDa,　SMP　＞　100kDa　concentration,　EPS　＜　1kDa,　EPS　＞　100kDa　specific　concentration　and　decrease　of　PSD　resulted　in　the　sludge　filterability　deterioration,　accelerating　membrane　permeability　decline　and　shortening　of　sustainable　operational　cycle,　whereas　FT-IR　analysis　of　membrane　surface　foulants　showed　that　SRT　had　no　significant　effects　on　the　compositions　and　refractive　index　of　infrared　spectroscopy　presented　the　consistence　with　the　amounts　of　SMP　and　EPS.　©　2016,　Editorial　Board　of　China　Environmental　Science.　All　right　reserved.