A　bench-scale　UCT-type　submerged　membrane　bioreactor　was　utilized　to　treat　synthetic　municipal　wastewater　with　foucus　on　the　influences　of　ρ(COD)/ρ(TN)　on　biological　nutrients　removal　and　membrane　fouling.　Results　show　that　the　process　has　a　strong　capability　of　anti-shock　organic　loading　and　average　89.9%　of　organic　matter　is　removed,　indicating　chemical　oxygen　demand　(COD)　removal　is　irrespective　of　ρ(COD)/ρ(TN)　ratio.　The　average　removal　efficiencies　of　total　nitrogen　(TN)　and　total　phosphorus　(TP)　under　ρ(COD)/ρ(TN)　ratio　of　7.3　are　the　highest　at　90.27%　and　92.4%　respectively.　Futhermore,　proportions　of　TN　removal　via　aerobic　simultaneous　nitrification　and　denitrification　(SND)　and　total　phosphorus　removal　via　anoxic　phosphorus　removal　increase　to　27.9%,　44.91%　from　1.6%,　7.94%　(ρ(COD)/ρ(TN)　ratio　of　3.2　to　7.3)　respectively.　Higher　fouling　rate　is　observed　with　the　increasing　ρ(COD)/ρ(TN)　ratio　which　changes　the　nitrogen　removal　pathway.　The　increase　of　organic　loading　and　decrease　of　dissolved　oxygen　induce　the　aerobic　SND　behavior　that　affect　the　phychemical　properties　and　metabolic　productions　of　aerobic　biosolids.　The　sludge　filterability　deteriorate　due　to　higher　extracellular　polymeric　substances　(EPS)　concentration　normalized　against　mixed　liquor　suspended　solid　(MLSS)　and　soluble　microbial　products　(SMP)　concentration　under　SND　condition,　which　also　result　in　higher　modified　fouling　index　(MFI)　values　both　for　suspendeded　solids　and　soluble　components.　Bio-floc　sizes　decrease　slightly　under　the　backgroud　of　the　high　air　shear　stresses　owing　to　the　decreased　dissolved　oxygen.　Correlation　between　the　fouling　rate　and　the　nitrogen　reduction　across　the　membrane　via　dinitrification　of　biofilm　attached　on　the　membrane　surface　is　also　assessed.