The electronic structures, surface energies and thermodynamic properties of different terminated Nb₂Al (100) surfaces were studied using first-principle calculations based on density functional theory. Results show that the calculated electronic structures present the enhanced metallic character and decrease covalent character for all terminated surfaces, which are attributed to the surface relaxations and the formation of surface states. According the calculated surface energies of different terminations, the surface stabilities of non-stoichiometric surfaces were analyzed. The C terminated surface (Nb₂₂Al₁₂) is the most thermodynamically stable surface under both Nb-rich and Al-rich conditions. Moreover, the work function of Nb₂Al (100) surface was calculated, indicating that its ability to gain and lose electrons on the surface is similar to that of pure elemental surface before formation.