Abstract: Recent developments of Mg2Si films are reviewed. On the basis of the crystal structure of Mg2Si, the basic properties, preparation methods, and application prospects of the films are presented. The researches show that Mg2Si is a kind of semiconductor with narrow-band-gap, which has good applications in photovoltaic and thermoelectric devices. Furthermore, the film is a new kind of environmental-friendly semiconductor material, and because the compositions of elements are rich in strata and non-toxic pollution, the materials attract great attention. In the technique of epitaxial growth, the relatively mature methods include molecular beam epitaxy, pulsed laser deposition, reaction-diffusion and so on. However, these methods have the problems of harsh preparation and poor quality of the thin film. Finally, current problems and future research trends of the materials are briefly discussed.