In this work, the lubrication mechanisms of Nb-contained oxides were revealed by using the density functional theory (DFT) computation. Concretely, a series of Nb-contained oxides, e.g. Nb2O5, AgNbO3 and NiNb2O6 were generated through tribochemistry during the friction process of the fabricated NiAl/Nb/Ag coatings as the temperature was increased, and the friction coefficients decreased from 0.51 to 0.54 at low temperatures to 0.24 - 0.27 at elevated temperature. Computational results showed that the binding energy of the Nb - O bond (-15.3 eV) in Nb2O5 was much higher than those of the Ag - O (-0.59 eV) and Ni - O (-0.90 eV) bonds in AgNbO3 and NiNb2O6, indicating that the latter Ag - O and Ni - O bonds were much easier to be fractured or broken under the friction force. AgNbO3 and NiNb2O6 registered better lubrication performances than Nb2O5, which could account for the excellent tribological performance of the coatings at elevated temperatures. This investigation contributes to revealing the high-temperature lubrication mechanisms of Nb-contained oxides.