In order to reveal the physical nature of high temperature oxidation of Nb alloy in electron level, the density of states, the atomic embedded energy, the atomic affinity energy and other electronic structure parameters of Nb alloy are calculated by using the recursive method. The high-temperature oxidation mechanism of Nb alloy is investigated. The results show that the diffusion rate and the solid solubility of oxygen are high in the Nb alloy, so oxygen can easily react with Nb to form oxides, which makes the oxidation resistance of Nb alloy poor at high temperatures. The calculated results of atomic embedded energy show that the stabilities of alloying elements (Ti, Si, Cr) are lower in the matrix than in the surface of Nb alloy, so they diffuse easily in to the surface of Nb alloy to form a surface layer enrichment with Ti, Si, Cr. Alloying elements Nb, Ti, Si, Cr have negative affinity energies to oxygen in alloy surface layer, thereby forming the corresponding oxide film, which has a protective effect for Nb alloy.