In this paper, the laser brazing of diamond abrasives using Ni-based solders in an Ar atmosphere was investigated. The microstructure and phase composition of interfaces between diamond abrasives and Ni-based solders were analyzed using scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Meanwhile, the formation mechanism of carbides at interfaces between solders and diamond abrasives was discussed. The results indicate that during laser brazing, the Cr-enriched layer around the diamond surface reacts with the C in the diamond surface and consequently forms Cr3C2. Based on reaction thermodynamics and kinetics analysis, it is revealed that the interface reaction products can be formed via replacement reactions, which realizes the tight combination between diamond abrasives and solders.