Ti-coated diamond is brazed in vacuum with heating temperature 920℃ for dwell time 8 min by using Ag-Cu-Ti alloy as filler. The interfacial microstructure, elements distribution and newly-formed phases are detected by X-ray diffraction, scanning electron microscope and energy dispersion spectrometer. The results show that during brazing, the delamination phenomenon in the interfacial layer takes place with the thickness of original coating and new layer about 0.8 μm and 5 μm, respectively. Newly-formed compound grows in form of short needle and into the shape of flake orderly on the coating surface. There is needle carbide about 4 μm long and 1.5 μm wide at the coating breakage, while the rod carbide grows from the plating at the edge. Atomic diffusion dynamic analysis shows that crystal structure limits the random motion of free C, making nucleation of newly-formed TiC evenly disperse and develop.