Herein, the graphitic carbon nitride (g-C3N4) nanosheets are protonated treatment and then electrostatically self-assembled with reduced graphene oxide (RGO) to obtain g-C3N4/RGO nanocomposite. When employed as a lubricant additive, the amino groups in g-C3N4 can accelerate the formation of friction films, while the cataclastic RGO nanosheets can repair worn surface and reduce wear. Meanwhile, the weak interaction between g-C3N4 and RGO sheets possesses low shear stress, producing interlayer slip, which can effectively reduce friction and anti-wear. As expected, the coefficient of friction (COF) of 0.103 and the wear volume of 0.86 × 105 μm3 for the lubricant containing 2.0 wt% g-C3N4/RGO are 62.3 % and 96.0 % lower than PAO-10 base oil, respectively.