The astonishingly distinct lubricity difference between the ionic liquid modified carbon nanoparticles grafted by anion and cation moieties (A-g-CNPs and C-g-CNPs) was well established as additives of polyethylene glycol (PEG200). The peripheral anion moieties and positively charged inner parts of C-g-CNPs could successively absorb onto the friction interfaces by electrostatic interactions to form the organic—inorganic electric double layer structures, tremendously boosting the lubricity of PEG200. Contrarily, the preferentially electrostatic adsorption of negatively charged inner parts but repulsion of the peripheral cation moieties determined the weak embedded stability of A-g-CNPs between the friction interfaces, even impairing the lubricity of PEG200. This work can offer solidly experimental and theoretical guidance for designing and developing the high-performance nanoadditives modified by ionic molecules.