Abstract: Ni-doped muscovite (Mu) composite particles (Mu/Ni) were prepared by a liquid phase reduction method. The morphologies, phase composition and elementary composition of the particles were characterized by scanning electron microscopy, x-ray diffraction and energy dispersive spectroscopy. The tirbological properties of Mu/Ni and Mu as lubricant additives for lithium grease were investigated and compared using a block-ring tribotester. The roughness, 2D and 3D morphologies and elementary composition of worn surface were analyzed to explore the friction-reduction and anti-wear mechanism. The results show that the Ni nanoparticles were evenly distributed on the surface of muscovite. Both Mu/Ni and Mu effectively improved the tirbological properties of lithium grease and Mu/Ni presented better friction-reduction and anti-wear performance than that of Mu. The friction coefficient was decreased by 67.9% as compared to lithium grease. The excellent tribological performance of Mu/Ni was attributed to the layer structure of muscovite as well as the formation of lubricating film composed of elements O, Fe, Si, Al and Ni on the worn surfaces.