Abstract: Brazing diamond tools has the characteristics of high protrude and strong bonding,which will be significantly degraded in brazing with the excessively high temperature,and so the thermal damage for the diamond was analyzed.The diamond was brazed in vacuum by using Ni-Cr alloy,then the surface of sample was observed by SEM and EDS,and the heat stress and graphitization on the surface were detected with Laser Raman spectroscopy.The results show that more carbide,such as Cr₃C₂,Cr₇C₃,exists on the diamond surface,and a little graphitization and chemical soakage take place on the surface.The tensile stress in the top of diamond is 110 MPa,and the compressive stress in the bottom of diamond is 520 MPa.