Abstract:NiCr alloy adding with Ni/C of 3%, 5% was utilized to braze diamond grains in protective furnace with the temperature 1 050 ℃ and holding time 5 min, respectively. Diamond morphology and the brazed joint microstructure were analyzed with the help of scanning electron microscope; the brazed joint hardness was measured by Vickers. The results show that NiCr alloy adding with Ni/C has good wettability with diamond; it could achieve high strength bonding between diamond and brazing layer. Carbide crystallizes and nucleates on the surface of diamond has an orientation relationship with diamond surface. The Cr7C3 morphology is hollow and clusters eutectic graphite forms in the brazing layer, which has a relationship with the adding Ni/C. There is small amount of Ni/C within brazing layer, the brazed joint hardness falls from 830 HV0.2 to 700 HV0.2, this is benefit to decrease the thermal stress and improve the protrusion of diamond in the later grinding.