Based on the empirical electron theory (EET) of solids and molecules, the valence electron structure (VES) and theoretical bond energy of MoSi2 was calculated by the bond length difference method (BLD). According to the average atomic model in substitutional solid solution of EET, the VES and theoretical bond energy of (Mo-0.95, Nb-0.05)Si-2 were analyzed. The results indicated that the Nb alloying into MoSi2 changed the hybridization state of Mo and Si atom, which correspondingly changed the parameters of VES. The ratio of covalent valence electron number to total number of valence electron in MoSi2 is 65.87%, compared with that of MoSi2, the ratio increase to 80.61% in (Mo-0.95, Nb-0.05)Si-2, thus the addition of niobium can improve the strength of MoSi2. The lattice electron decrease from 4.7141 to 2.5526, which reduced the plasticity of MoSi2 by niobium microalloying. (C) 2011 Elsevier B.V. All rights reserved.