Polycrystalline Fe3O4 film grown directly on a Si(100) substrate and on a tantalum (TO buffer layer have been prepared by direct current (dc) magnetron-reactive sputtering and vacuum annealing under an infrared-lamp furnace system. The Fe3O4 quality was examined by x-ray diffraction (XRD). The results showed that the polycrystalline Fe3O4 films fabricated on a Ta buffer layer were better than directly sputtering the film on a Si substrate after annealing. The annealing temperatures were also investigated carefully. The optimum annealing temperature was found at 300 degrees C. The negative magnetoresistance was tested in polycrystalline Fe3O4, and showed a very weak saturation trend in the magnetic field up to 400 Oe. (c) 2005 American Vacuum Society.