A　bench-scale　UCT-type　submerged　membrane　bioreactor　was　operated　to　treat　synthetic　municipal　wastewater　regarding　the　influences　of　aeration　and　recirculation　ratios　on　process　performance　and　membrane　fouling.　The　results　show　that　variations　of　aeration　intensity　and　recirculation　rations　in　UCT-MBR　process　have　no　effects　on　the　COD　and　NH4+-N　removals,　with　removal　efficiencies　of　COD　(chemical　oxygen　demand)　and　NH4+-N　stabilizing　at　89.4%　and　99.7%　on　an　average　and　with　effluent　concentrations　of　31.8　and　0.2　mg/L　respectively.　In　the　feed　condition　of　ρ(COD)/ρ(N)/ρ(P)　at　49.1/8.31/1.0,　the　increase　of　recirculation　ratio　(r1　from　200%　to　400%)　strengthens　the　denitrifying　phosphorus　removal,　during　which　in　the　condition　of　lower　aeration　intensity　(100-125　L/h,　ρ(DO)=1-2　mg/L)　and　the　recirculation　ratio　of　400%,　the　ratio　of　DPAOs　to　PAOs　reaches　the　maximum　value,　and　stabilizes　at　about　50.7%.　The　increase　of　the　aeration　intensity　(250-300　L/h,　ρ(DO)=2-3　mg/L)　inhibits　anoxic　phosphorus　removal　efficiency　(Rano-p)　and　removal　efficiencies　of　TP　and　TN,　decreasing　to　78.0%,　77.0%　and　70,0%　from　93.0%,　92.6%　and　79.6%　respectively.　Furthermore　certain　positive　correlations　between　effluent　concentrations　of　TN　and　TP,　removal　efficiencies　of　TN　and　TP　are　observed　(R12=0.6360;　R22=0.6786).　In　addition,　the　increase　of　the　aeration　intensity　induces　the　increase　amount　of　Bound-EPSs　(bound　extracellular　polymeric　substances,　Bound-EPSs),　whereas　the　scouring　effect　of　the　gas-water　two-phase　flow　significantly　reduces　the　resistance　of　the　cake　layer;　the　increase　of　recirculation　ratio　(r1　from　200%　to　400%)　also　increases　shear　stress　for　activated　sludge　resulting　in　the　decrease　in　particle　size　and　the　increase　of　SMPs　(soluble　microbial　productions,　SMPs),　which　become　the　main　reason　for　the　increased　resistance　of　deep　pore　clogging.　FT-IR　(Fourier　translation　infrared　spectroscopy,　FT-IR)　analysis　of　the　membrane　foulants　shows　that　the　variations　of　aeration　intensity　and　the　recirculation　ratios　have　no　effects　on　their　compositions.