Residual stress is the main factor affecting the machining performance and service life of brazed diamond tools. At present, in simulations, diamond is often simplified as a spherical shape, which leads to changes in the degree of structural constraint at the joint, resulting in significant differences between the calculated results and the actual situation. The evolution law and distribution characteristics of residual stress in vacuum-brazed diamonds, as well as the influence of residual stress on wear resistance, were investigated. Firstly, the geometric model of the diamond coating was optimized based on macroscopic morphology. Then, a finite element model of the stress field of vacuum brazed diamond coating was established using thermal elastoplastic mechanics, and the stress field distribution law of the diamond coating was obtained. Subsequently,residual stress measurement experiments were conducted on diamond and nickel based coatings to verify the reliability of the model. Finally, the influence of residual stress on the wear resistance of diamond coatings was explored through wear-resistant weight loss experiments. The main form of wear failure of diamond tools is diamond detachment caused by insufficient grip of the coating on diamond abrasive particles. The diamond wrapped by the brazing material layer is mainly affected by residual compressive stress, which increases the coating’s grip on the diamond. The higher residual stress inside the nickel based coating can also effectively suppress the wear-resistant failure mode of coating peeling.