Composite　nanofiltration　(NF)　membranes　with　anti-bacterial　activity　were　prepared　by　electrostatic　self-assembly.　A　novel　composite　(Ag+-PEI/　Cu2+-PEI/　Fe3+-PEI)　was　obtained　by　the　chelate　reaction　of　polyethylenimine　(PEI)　with　metal　ion,　which　constituted　the　main　component　of　the　separation　layer　of　the　prepared　membrane.　Three　composite　(Ag+-PEI/　Cu2+-PEI/　Fe3+-PEI)　NF　membranes　prepared　at　optimized　condition　exhibited　excellent　permeability　(121　L.m(-2).h(-1).MPa-1/71　L.m(-2).h(-1).MPa-1/　73　L.m(-2).h(-1).MPa-1)　and　high　rejection　(96.5%/　94.5%/　91.6%)　for　acid　fuchsin　as　well　as　low　rejection　(31.5%/　27.5%/　23.7%)　for　MgSO4.　Meanwhile,　the　higher　flux　recovery　ratio　(FRR)　of　dye　was　observed　for　the　Fe3+-PEI　membrane　(FRRFe=91.5%)　than　that　for　others　((FRRCu=83.2%)　and　(FRRAg=76.4%)).　Furthermore,　these　three　NF　membranes　also　presented　good　hydrophilicity　(59　degrees/39　degrees/35　degrees),　excellent　anti-bacterial　activity　(up　to　95%　against　E.　coil　and　over　90%　against　S.　aureus)　and　good　long-term　stability　in　our　trails.　These　results　were　of　great　significance　for　dye　recycle　in　industrial　field.　(C)　2019　Taiwan　Institute　of　Chemical　Engineers.　Published　by　Elsevier　B.V.　All　rights　reserved.