In order to improve the lubrication performance of the WS₂-based coatings at elevated temperature, the mechanisms of enhancing the tribological performance of WSNb coatings at elevated temperatures are investigated. The WSNb coating doped with 11.9 at.% Nb exhibited excellent anti-friction and wear resistance, achieved a low coefficient of friction of 0.02 at 400 °C, and its wear resistance was much better than that of WS₂-based coatings. The Nb metal and its sulfide in the coating are more sensitive to oxygen than WS₂ at 400 °C, which reduces the oxygen concentration between the friction pairs and protects the WS₂ lubricating phase from being oxided. In addition, Nb enhances the hardness and Young's modulus of the coatings through the solid solution strengthening effect, generating a more continuous and stable lubricating film during the silding process. First-principles calculation results demonstrated that the Nb spontaneously forms Nb-S bonds with S atoms in the coating. The molecular details of the Nb-S formation have been investigated in depth.