Extracellular　polymeric　substances　(EPSs)　in　activated　sludge　suspensions　are　the　key　substances　leading　to　the　membrane　fouling.　In　order　to　understand　the　effect　of　EPSs　on　the　membrane　fouling,　the　actual　EPSs　solution　extracted　from　activated　sludge　suspensions　was　used　as　the　feed　solution　to　conduct　dead-end　microfiltration　experiment　under　different　pressures　by　using　different　membranes.　The　flux　(J),　fouling　resistances　(R-m,　R-p,　R-c　and　R-total)　and　the　available　membrane　area　(A/A(0))　were　used　to　describe　the　membrane　fouling.　The　results　showed　that　with　the　increase　of　pressure,　J　and　R(total　)increased.　R-p　firstly　increased　and　then　kept　constant,　R-c　always　increased　and　became　the　dominant　resistance.　A/A(0)　decreased　from　1　to　a　constant.　R-c　plays　a　key　role　on　R-total　for　different　membranes　under　the　same　pressure.　The　sequence　of　the　steady　available　membrane　area　(A(steady)/A(0))　for　different　pressures　was:　63.0%　(0.05MPa)＞　56.5%　(0.08MPa)＞　53.6%　(0.10MPa),　and　that　for　different　membranes　was:　80.1%　(0.2　mu　m　PES)　＞　79.9%　(0.1　mu　m　PES)　＞　78.4%　(0.1　mu　m　PAN)　＞　53.6%　(0.1　mu　m　PVDF).