Abstract: The brazed diamond samples with Ni-Cr filler alloy were prepared by vacuum brazing method.The microstructure of graphite and the degree of graphite on diamond surface were analyzed by scanning electron microscope(SEM), energy dispersion spectrometer(EDS) and laser Raman spectroscopy.The results show that graphite grows on the surface of the diamond during vacuum brazing, diamond with Ni-Cr filler alloy and its thickness is about 10 μm.The reason of graphitization on brazed diamond surface is that there is degradation of atomic carbon on diamond surface in the molten Ni-Cr filler alloy during brazing, and there are precipitation and recrystallization of atomic carbon from the Ni-Cr filler alloy.The formation of graphite is earlier than the formation of carbide during vacuum brazing.