Abstract: The triblock amphiphilic polylactic acid copolymer of poly(N-vinylpyrrolidone)-block-polylactic acid-block-poly(N-vinylpyrrolidone)(PVP-b-PLA-b-PVP) was synthesized by atom transfer radical polymerization(ATRP), which was blended with polyvinylidene fluoride (PVDF) to fabricate a new type of modified PVDF membrane. Results showed that the surface of PVDF membrane was compact. The finger-like holes and the sponge-like holes coexisted in the cross section of membrane. However, the modified PVDF membrane contained plenty of holes in the surface with finger-like holes which penetrated its cross section. Moreover, compared with PVDF membrane, the blend membrane had a significant increase by 158.87% in water flux, a reduction in the contact angle by 16.7%, and a reduction in the anti-pollution index by 64.7%.