Titanium plating on the surface of diamond powder can improve its wettability to the bonding agent, and the preparation process of titanium plated metal layer is of great significance to the industrial application of diamond powder. The effects of different titanium powder particle sizes (60 mesh coarse powder and 325 mesh fine powder) and raw material ratios on the process of vacuum and protective atmosphere titanium plating on the surface of diamond powders were compared. The chemical composition of the titanium coated diamond powder surface was characterized by XRD as diamond, Ti and TiC transition layer, and the morphology of the titanium coated diamond powder and the distribution of surface elements were analyzed by SEM, which showed that Ti coating on the surface of diamond particles could be achieved with different ratios and Ti powder particle sizes. The Raman spectra of fine Ti-coated diamond contain characteristic peaks of diamond and Ti, while the Raman spectra of coarse Ti-coated diamond and Ti-coated diamond synthesized in vacuum atmosphere are affected by the ratio of raw materials. The UV-visible absorption spectra showed that the Ti-coated diamond had obvious absorption peaks in the wavelength region of 228-234 nm and 328-350 nm, respectively. The weight loss rates of vacuum synthesized titanium-coated diamond and fine-grained Ti-coated diamond were lower than those of coarse-grained Ti-coated diamond. Combined with the results of Raman spectroscopy, ultraviolet absorption spectroscopy and thermal analysis, the performance of fine Ti coated diamonds under argon atmosphere protection is better than that of coarse Ti powder coated diamonds and vacuum atmosphere coated diamonds.