Abstract: In this paper, an amphiphilic copolymer (PVDF-g-PAA) having poly(vinylidene fluoride)(PVDF) backbones and poly(acrylic acid)(PAA) side chains was synthesized via radical polymerization method in water/ethanol mixed solution to improve the hydrophilicity of PVDF membrane. Three PVDF-g-PAA copolymer samples of defferent grafting percentage (GP) were prepared by varying the concentration of AA. The results of Fourier transform infrared (FT-IR) and thermogravimetric analysis (TGA) indicate the GP at 10% AA concentration was the maximum among them. The copolymer was cast into membrane via immerse precipitation method. Scanning electron microscopy (SEM)、water contact angle measurement and filtration experiment were applied to evaluated the morphology and performance of membranes. It was found that mean pore size and porosity of modified membranes were increased with the increase of GP, but the contact angle of modified membranes decreased, indicating an improved hydrophilicity. Under high separation performance, the water flux and flux recovery ratio of modified membranes were enhanced by 3.78 times and 0.76 times, respectively, which means the permeate ability and fouling resistance of modified membrane have been great improved.