Covalent immobilization of polycations onto a membrane surface has been shown to significantly improve the resistance to biofouling. The poly(vinylidene fluoride)-graft-poly(N,N-dimethylamino-2-ethylmethacrylate) (PVDF-g-PDMAEMA) copolymer was synthesized via radical grafting copolymerization and fabricated into a flat membrane. The polycation membrane surface was constructed by quaternization of PDMAEMA side chains with 1,5-dibromopentane and diquaternization of 4,4-bipyridine. As revealed by membrane surface morphology, pore size, and porosity measurement, the polycations are distributed on the membrane surface and internal pore channel surface. Water contact angles confirm that the incorporation of polycations remarkably promotes the surface hydrophilicity of a membrane. The polycation membrane surface provides an excellent bactericidal efficiency against Escherichia coli.