On the basis of the first principle interatomic potentials, the site preference of various alloying elements in Fe3Al were evaluated for Ti, Si, Ni, Mn, Mo, and Cr, respectively. The calculated results of the substitutional distribution were in good agreement with the experimental results. Moreover, the calculated results showed that H atoms in Fe3Al prefer to occupy the Fe-type octahedral interstice on the surface, which resulted in concentration of H atoms on the surface. Cr addition decreased the absorbability of Fe3Al-based alloys for H atoms and the force to drive H atoms segregating to surface. The concentration of H atoms on the surface can be decreased by Cr addition.