Poly(vinylidene fluoride) (PVDF) was modified by acetalyzed poly(vinyl alcohol) (PVAd) for preparing PVDF/PVAd blending ultrafiltration (UF) membrane through phase inversion method. PVAd was synthesized from acetalization of poly(vinyl alcohol) (PVA) by acetaldehyde (Ad) under acidic conditions. PVDF/PVAd membrane was characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier-transform infrared spectrometer (FT-IR), water contact angle and scanning electron microscope (SEM). The good compatibility between PVDF and PVAd was proved by DSC analysis. The water contact angle measurements demonstrated that the hydrophilicity of PVDF/PVAd membrane was enhanced than PVDF membrane. The influences of the composition of dope solution and the degree of acetalization (DA) of PVAd on morphology and permeation performance of PVDF/PVAd membrane were investigated. The results showed that the blending of PVAd significantly affected the pore structure and hydrophilicity of PVDF membrane, and consequently improved the anti-fouling performance of PVDF/PVAd membrane. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.