Fe/Si multi-layer films were fabricated on Si(100) substrates utilizing the radio frequency magnetron sputtering system. Si/β-FeSi2 structure was found in the films after the deposition. A series of characterization methods were employed, including transmission electron microscopy and high-resolution transmission electron microscopy, to explore the dependence of the microstructure of β-FeSi2 film on the preparation parameters. It was found that β-FeSi2 particles were formed after the deposition without annealing, whose size was less than 20nm and the band-gap was 0.94eV. After annealing at 850℃, particles grew larger， however, the stability of thin films was still good.