A series of PVDF-Fe3O4 ultrafiltration membranes with different amounts of Fe3O4 were prepared in a parallel magnetic field or without a magnetic field from suspensions, using the phase inversion process. A comparison of membrane properties was conducted. When the Fe3O4 content in a membrane was below 65 wt%, both of the Fe3O4 content and the magnetic field used during the formation of membrane had no dramatic influence on the flux and the fouling-resistance ability of a PVDF-Fe3O4 ultrafiltration membrane. However, the initial rejection of a PVDF-Fe3O4 ultrafiltration membrane increased with the Fe3O4 content in a membrane. When the Fe3O4 content in a membrane reached 65 wt%, the external magnetic field forced magnetic Fe3O4 particles in a casting solution to arrange along the direction of the magnetic field during the membrane formation. As a result, a novel membrane with "lamellar macrovoids" in the sublayer could be prepared. The PVIDE-Fe3O4 membrane of 70 wt% Fe3O4 with "lamellar macrovoids" in the sublayer had the best comprehensive performance in terms of pure water flux, rejection and fouling- resistance and compaction-resistance ability. (C) 2012 Elsevier B.V. All rights reserved.