The valence electron structures of Al2Ca and Mg2Ca, and the interface electron structures of Al2Ca(111)//α-Mg(), Mg2Ca(001)//α-Mg(0001) are calculated and analyzed based on the empirical electron theory of solids and molecules and an improved Thomas-Fermi-Dirac(TFD) theory. The strongest bond (nA=0.397 06) of Al2Ca and the secondary strong bond (nA=0.302 45) of Mg2Ca greatly hinder the dislocation movement and grain-boundary sliding, so that the alloy’s intensity is enhanced. Compared the FV value of γ-Mg17Al12 (＝44.22), the total bond-forming ability in unit volumevalue of Al2Ca and Mg2Ca is 99.25 and 47.66, respectively. It shows that the high temperature stability of Al2Ca is better and its existence is advantageous to improve the high temperature performance of Mg-Al alloy. The interface electronic density difference of the second phase in crystal boundary and the substrate is greater than that of the γ-Mg17Al12(110)//α-Mg(0001), the γ-Mg17Al12 and the substrate, with a better interface strengthening effect effectively to increase the operation temperature of Mg-Al alloy. The bigger difference of the interface electron densities would prevent grain growth and a finer microstructure can be obtained during solidification, as a result, the nucleation rate of γ-Mg17Al12 is increased and the mechanics properties of Mg-Al alloy are enhanced.