this invention provides a polymeric separation membrane that has excellent durable antibacterial effect and stain resistance , and a preparation method thereof . the polymeric separation membrane can be widely applied for water treatment , which belongs to the field of water treatment and membrane separation science and technology . the polymeric separation membrane containing quaternary ammonium salt is prepared by the immersion precipitation phase inversion method , using quaternary ammonium salt mixed with polymer and additives . this modification method effectively improves the antibacterial and antifouling ability of the polymeric separation membrane prolongs the service life of membranes and significantly inhibits the reproduction of bacterial and microbial . the preparation method has the advantages of simple process , easy operation , easy for promotion , and also avoids expensive equipment . the polymeric separation membrane has great antibacterial ability and stain resistance , therefore , it has potential application in the field of water treatment .