To study the anti-oxidation mechanism of WS₂ films, the pure WS₂, and Al doped WS₂ composite films were prepared via radio frequency sputtering and the atomic oxygen (AO) irradiation tests were conducted using a ground AO simulation facility. The tribological properties of both films before and after AO irradiation were evaluated using vacuum ball-on-disk tribo-tester. The incorporation of a small fraction of Al dopant resulted in microstructure change from loose columnar platelet with significant porosity for pure WS₂ film to very dense structure. In pure WS₂ film, WS₂ exists as crystalline phase with edge-plane preferential orientation, but nanocrystalline and amorphous phase coexists for the WS2-Al composite film. Even if large amount of AO transported into the interior through the longitudinal pores, the pure film showed good AO irradiation resistance owing to the basal plane of WS₂ crystal exhibiting much higher anti-oxidation capacity than the edge-plane. The composite film also had excellent AO irradiation resistance due to the formation of effective thinner WO₃ cladding layer in the sub-surface layer. Tribological results revealed that the composite films showed a significantly improved wear resistance, in comparison to the pure WS₂ film. Besides, due to the effective AO resistance, the tribological properties of WS₂ films remained almost unchanged before and after AO irradiation.