Abstract: The nanocomposites of graphene/MoS₂ (RGO/MoS₂-1 and RGO/MoS₂-2) of different morphological structures were prepared by hydrothermal method. Their morphology, chemical composition and crystal structure were examined by electron microscope, Raman, X-ray diffraction and thermogravimetric analysis. Furthermore, the tribological properties of RGO/MoS₂-1 and RGO/MoS₂-2 in PAO-4 were tested by using an SRV-IV tribometer. Results show that the interlayer spacing of RGO/MoS₂-2 was larger than that of RGO/MoS₂-1 because of the flower-like structure, and RGO/MoS₂-2 exhibited better tribological property. The characterization of the lubrication mechanism was confirmed by Raman and X-ray photoelectron spectrometer, showing that the excellent tribological properties of RGO/MoS₂ composite nano-additives were attributed to the synergistic effect of adsorption and tribochemical reactions.