The metastable phases of Fe1- x Sn x alloys were stabilized by their epitaxial growth on MgO(100). The Fe1- x Sn x alloys with a body-centered-cubic-based structure were realized in the range of 0 ≤ x ≤ 0.4. For x = 0.25, the B2 structure was observed by transmission electron microscopy and X-ray diffraction analysis, although the hexagonal D019 structure was a thermodynamically stable phase. With respect to magnetic properties, all the compositions show similar hysteresis curves except for x = 0.25. According to ab initio calculations, D03-Fe3Sn and B2-Fe3Sn have band structures similar to that of Fe, which results in a large tunnel magnetoresistance by coherent tunneling.