Asymmetric and charged ultrafiltration membranes were prepared from blends with synthesized polyacrylonitrile (PAN) and hydrophilically modified polyacrylonitrile by the classical phase inversion technique in water. As hydrophilically modified polyacrylonitrile was added, the membranes were more hydrophilic and better anti-fouling performance. Collagen extract was separated by the resulted ultrafiltration membranes. The results showed that, compared to the pure PAN ultrafiltration membrane, the blend membrane possessed higher hydrophilicity and better anti-fouling property. Fouling of collagen particles on the blend membranes was able to reduce as the composition of hydrophilic polyacrylonitrile increased. And the resulted membrane can be used to purify and concentrate collagen extract effectively. The pH of the collagen extract and the hydrophilic polyacrylonitrile content in the blend membrane could influence the membrane separation performance during separating the collagen extract. (C) 2009 Published by Elsevier B.V.