Two oil-miscible ionic liquids (ILs) with different anions, phosphate (N88816P4) and phosphorothioate (N88816SP4), were applied in PAO10 as lubricating additives. Adsorption layers and tribofilms formed at the interface With ILs, which facilitated transition from adhesive to abrasive wear and enhanced the tribological performance. Moreover, N88816SP4 outperformed N88816P4, especially at elevated temperature and under extremely high pressure. As revealed by density functional theory (DFT) calculation and transmission electron microscopy (TEM) analysis, S-containing anions not only enhanced the adsorption of ILs, but also participated into the tribochemical reaction, resulting in a tribofilm consists of iron oxides and sulfides. As the temperature increased, the content of sulfides increased, leading to superior tribological performance.