The epitaxial films of Mg2Si on Si(111) substrate were prepared with different sputtering power by RF magnetron sputtering system. The crystal structures and the surface morphology of the Mg2Si films were characterized by X ray diffraction (XRD) and the field emission scanning electron microscope (FESEM). The epitaxial growth characteristics of Mg2Si films on Si(111) substrates are obtained by theoretical analysis. The results show that, with increasing sputtering power from 80 W to 110 W, the Mg2Si films have one preferential growth feature of Mg2Si(220) and with increasing the sputtering power the intensity of the diffraction peak of Mg2Si film increase firstly, then decreases. The diffraction peak intensity of Mg2Si film was up to the strongest when the sputtering power was 100 W.