Acryl amide (AAm) was grafted onto poly (vinylidene fluoride) (PVDF) powder by a γ-rays pre-irradiation induced graft polymerization technique. The ,DG, values of the PVDF-g-PAM powder were determined by fluorine elemental analysis. Effects of grafting time on ,DG, of PVDF-g-PAM powder at the same monomer concentration were studied. And modified powder was dissolved in NMP and added PVP as pore-forming agent. The microfiltration (MF) membranes were cast using a phase inversion method. The contact angle, degree of swelling, water flux and antifouling properties of those modified MF membranes were investigated. The results indicated that the hydrophilicity of modified MF membranes was improved obviously and the antifouling property of modified MF membranes (,DG, of 13%) was better than that of the pristine membrane.