Abstract: Using diamond, high-purity tungsten powders, and tungsten oxide powders as the raw materials, the tungsten coatings were fabricated on the diamond surfaces by thermal diffusion method. The microstructure, phase composition, and element distribution of the coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The coating mechanism was analyzed, and the effects of coating temperature and raw material mass ratio on the coating quality were investigated. The results show that, the uniform, continuous, and dense tungsten coatings can be formed on the diamond surfaces by thermal diffusion method, showing the gradient structure of WC–W₂C–W. The relative density of the coatings increases with the rise of coating temperature, and the optimal coating quality is obtained at 1150 ℃. The mass fraction of tungsten in the coatings first increases and then decreases as the proportion of tungsten in raw materials rises. When the raw material mass ratio (diamond, high-purity tungsten powders, tungsten oxide powders) is 1.0:1.2:1.0, the coatings on the diamond show the uniform and dense structure with fine and closely arranged grains, delivering the excellent overall quality. The optimal preparation parameters are determined as the coating temperature of 1150 ℃, holding time of 1 h, and raw material mass ratio of 1.0:1.2:1.0. The coatings prepared under these conditions possess the best comprehensive properties.