A hydrophilic negatively charged nanofiltration membrane was prepared by UV irradiation two-step graft polymerization of hydroxyethyl methacrylate(HEMA) and sodium styrene sulfonate(SSS) onto the surface of ultrafiltration membranes made of polyethersulfone(PES-C).The effect of the irradiation time on the membrane performance was studied by measuring the salt retention through the membrane.The results show that the composite nanofilration has high retention and permeation flux to high valent anionic salts.The sodium sulfate of the membrane,which was grafted by HEMA for 120 s and then SSS for 15 minute,shows rentention beyond 95% and 19.02 L/(m2·h).