Abstract: Oil-soluble ionic liquids have broad prospects in aerospace, mechanical industry and vehicle engineering due to their excellent thermal stability, viscosity-temperature properties, anti-corrosion properties and tribological properties, of which tribological properties are one of the important indicators for evaluating the performance of oil-soluble ionic liquids. This paper summarises the types of common oil-soluble ionic liquid anions and cations and discusses the progress of research on their tribological properties when used as lubricant additives under steel/steel, steel/copper, steel/light alloys and ceramic friction substitutes, as well as the current status of research on the comparison of the tribological properties of oil-soluble ionic liquids with those of commercial lubricant additives. In addition, the mechanism of friction reduction and anti-wear action at the friction sub-interface of oil-soluble ionic liquids was summarised, and the prospect of its application was outlooked.