Abstract: Eight modified graphene oxides were prepared by the surface functionalization of multilayer graphene oxide (MGO) and few layer graphene oxide (FGP) with four long chain amines as modifiers. Effects of functionalization process on the microstructure and molecular structure of graphene oxides were investigated by FESEM, Raman, and FT-IR. The dispersion stabilities of modified GO in 150SN mineral oil were investigated to screen the optimum modification method. Moreover, tribological properties of modified GO as an additive in 150SN oil were evaluated by tribo-tester, and the wear mechanisms were analyzed by the morphologies and Raman spectra of the worn surfaces. The results indicated that four long chain amine modifiers can be successfully grafted onto graphene surface by amidation reaction. The dispersion stability of MGO was better than that of FGO, especially for MGO-OAM and MGO-PIB. Anti-wear and friction-reducing ability of FGO was better than that of MGO, and the modified MGO effectively facilitated the tribological performance of 150SN mineral oil. The wear mechanisms under different conditions include plastic deformation, abrasive wear and adhesive wear.