During sintering process of diamond tools, metal bond containing graphitizing elements such as Fe, Co, Ni seriously e-rodes diamond grits, which reduces the strength of the diamond grits. In this paper, silicon films were coated on the surface of dia-mond grits by means of atomic layer deposition (ALD) from gaseous SiH4. Fourier transform infrared (FTIR) spectra, X-ray dif-fraction (XRD) and Atomic force microscopy (AFM) were utilized to analyze the structure and the morphology of Si-coated dia-mond respectively. The results suggested that the film was cubic-phase polycrystalline silicon and the surface of the film was smoothand continuous. According with the adsorption mechanism of SiH4on the surface of diamond grits, the stretching and bendingmodes of SiH2and SiH3both existed. Differential thermal analysis (DTA) was used to compare the thermal stability of coated dia-mond and uncoated diamond. Owning to the protection of silicon films the starting oxidation temperature of coated diamond reachedas high as 920℃, which was much higher than that of uncoated diamond. Bending experiment was conducted to measure the ben-ding strength of Fe-Cu-Sn-Ni based metal bond diamond blade. In comparison with uncoated diamond, the bending strength of Si-coated diamond blade increased by16.2%, scan electron microscope (SEM) observation of the blade fracture revealed that the de-posited silicon films not only protected the diamond grits from erosion during sintering process but also realized the strong bindingbetween the diamond grits and the bond. During sintering process of diamond tools, metal bond containing graphitizing elements such as Fe, Co, Ni seriously e-rodes diamond grits, which reduces the strength of the diamond grits. In this paper, silicon films were coated on the surface of dia-mond grits by means of atomic layer deposition (ALD) from gaseous SiH4. Fourier transform infrared (FTIR) spectra, X- ray dif-fraction (XRD) and Atomic force microscopy (AFM) were utilized to analyze the structure and the morphology of Si- coated dia-mond respectively. The results suggested that the film was cubic-phase polycrystalline silicon and the surface of the film was smoothand continuous. According to the adsorption mechanism of SiH4on the surface of diamond grits, the stretching and bending modes of SiH2 and SiH3both existed. Differential thermal analysis (DTA) was used to compare the thermal stability of coated dia-mond and uncoated diamond. Owning to the protection of silicon films the starting oxidation temperature of coated diam Bending experiment was conducted to measure the ben-ding strength of Fe-Cu-Sn-Ni based metal bond diamond blade. In comparison with uncoated diamond, the was much higher than that of uncoated diamond. strength of Si-coated diamond blade increased by 16.2%, scan electron microscope (SEM) observation of the blade fracture revealed that the de-posited silicon films not only protected the diamond grits from erosion during sintering process but also realized the strong bindingbetween the diamond grits and the bond.