Abstract: Diamond grits was brazed to steel substrate by using Ni-based filler alloy via laser in an argon atmosphere.The brazed diamond grits were detected by scanning electron microscopes(SEM),X-ray diffraction(XRD) and energy dispersive X-ray spectroscopy(EDS).The formation mechanism of carbide layers between the brazing filler metal and the diamond was discussed.All the results indicate that high strength bonding between diamond grits and the steel substrate has been successfully realized because the chromium in the Ni-based alloy segregated preferentially to the surface of the diamond to form a chromium-rich reaction product,and the bond between the alloy and the steel substrate is established through a cross-diffusion of iron and Ni-based alloy.