In the present study, Fe and Si powders (3:1 in atomic proportion) were mechanical alloyed and subsequently treated under different anneal conditions. The changes of phase composition and structure during the mechanical alloying and following heat treatment processes were mainly studied. The results showed that the XRD peaks of Fe were gradually broadened and weakened with the increase of the milling time associated with the shifting from low angles to high angles, and the main phase changed into α-Fe (Si) solid solution after milling for 20h. When the product was heat treated below 400oC, the main phase remained α-Fe (Si). While it was treated above 400oC, ordered Fe3Si phase was found and the XRD peaks of Fe3Si became sharper with the further increase of the temperature.