Protic ionic liquid-modified nanosilica (SiO2-PIL) hybrid with excellent dispersion stability and thermal stability was prepared. The SiO2-PIL hybrid was used as a high temperature antiwear additive for pentaerythritol ester (PE) base oil, which exhibited better antiwear ability and load-carrying capacity at high temperature compared with triphenyl phosphate (TCP). This is attributed to the synergistic friction-reducing and antiwear effects of nanosilica and ionic liquid during sliding at elevated temperatures. Findings indicate that a protective tribofilm with sandwich structure composed of phosphate and amorphous carbon as the outer layer and silica nano -particles as the interlayer was formed on the worn surface. Finally, combined with the adsorption behavior and the results of worn surface analysis, the high-temperature lubrication mechanism of SiO2-PIL was proposed.