Abstract: NbSe₂/Ag nanocomposite i.e. Ag nanoparticles well-dispersed on the surface of NbSe₂ nanosheets, was successfully prepared by chemical reduction. UMT-2 friction and wear tester and scanning electron microscope were used to explore the tribological behaviors of NbSe₂/Ag nanocomposite as a lubricant additive for coal mine machinery. NbSe₂/Ag nanocomposite was better lubricating additive than Ag nanoparticles as well as NbSe₂. The lubricating effect of NbSe₂/Ag nanocomposite were attributed to four aspects: Firstly, according to the first simulation calculation of density functional theory, the order of the maximum shear strength from highest to lowest was NbSe₂/Ag nanocomposite, Ag, NbSe₂. Secondly, Ag nanoparticles prevented NbSe₂ from agglomeration and this was favorable for formation of uniform lubricating. Thirdly, Ag was soft with low elastic modulus, and NbSe₂/Ag nanocomposite was subjected to shearing to form a lubricating film. Ag nanoparticles distributed uniformly in the lubricating film, making the lubricating film difficult to break under the scraping effect of hard micro-bulges on the counterpart. Finally, some of Ag nanoparticles probably rolled on the contact interface as “micro bearings” to reduce friction coefficient. However, the lubricating effect of lubricating oil was not positively correlated with the addition amount of NbSe₂/Ag nanocomposite. In specific, friction coefficient decreased firstly and then increased with the increasing addition amount of NbSe₂/Ag nanocomposite. For addition amount of 1.5% NbSe₂/Ag nanocomposite, the lubricating oil showed the excellent tribological properties.