Fe/Si multi-layer films were fabricated on Si (100) substrates utilizing radio frequency magnetron sputtering system. Si/β-FeSi2 structure was found in the films after the deposition. Structural characterization of Fe-silicide sample was performed by 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 is less than 20nm ,with a direct band-gap of 0.94eV in room temperature. After annealing at 850°C, particles grow lager, however the stability of thin films was still good.