Poly(vinylidene difluoride) (PVDF)/Fe3O4 magnetic nanocomposite was prepared by a simple coprecipitation method, and was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and ultraviolet visible spectroscopy (UV-Vis). The SEM images showed that Fe3O4 nanoparticles were dispersed in the PVDF matrix as some aggregates with the sizes of 50 nm-2 mu m, and the XRD curves showed the incorporation of the Fe3O4 nanoparticles in PVDF matrices and the decrease of the crystallinity of the PVDF. VSM results showed that the saturation magnetization (M-s) and remnant magnetization (M-r) of the PVDF/Fe3O4 nanocomposite increased with the increase of the Fe3O4 content, and that Ms and Mr along the parallel direction were higher than those along the perpendicular direction at the same Fe3O4 content. The coerctive force (H-c) of the nanocomposite was independent of the Fe3O4 content and approximately equal along the parallel and perpendicular direction at the same Fe3O4 content. The optical band gap (E-g) of the PVDF/Fe3O4 nanocomposite was influenced by the Fe3O4 content, and decreased by 0.75 eV compared with that of pure PVDF when the Fe3O4 content was 3 wt %. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 1763-1768, 2009