In processing of manufacturing the brazing diamond bit for vacuum activation brazing-sintering machine, when the temperature exceed 727℃，the bit body of steel 45 will react austenitic reaction and becomes easy to deform under brazing-sintering pressure because of the higher Ni-based brazing temperature. In order to maintain certain pressure to reduce the contact electric resistance and meet the requirements of constant brazing sintering temperature, by increasing the flow area of the bit steel body and reducing the resistance of the steel part to reduce the heating power and the temperature rise of the bit steel body, the plastic deformation of bit body can be effectively reduced.