Abstract: Brazing diamond grits to 45 steel substrate using Ni-based filler alloy was carried out via laser in an argon atmosphere.The brazed diamond specimens were detected by scanning electron microscopy(SEM),X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS).All the results indicate that the chromium in the Ni-based alloy segregated preferentially to the surface of the diamond to form chromium-rich reaction products Cr3C2,Cr7C3,Cr23C6,and the bond between the alloy and the steel substrate is established through a cross-diffusion of iron and Ni-base alloy.