A firm joint between steel base and diamond was realized by using Ag-Cu-Ti brazing diamond in vacuum. The interface between diamond and filler and carbide formed on the diamond surface was analyzed by using SEM, EDS, XRD and Raman Spectroscope. Results showed that carbide layer was formed as a result of the reaction between Ti and diamond, and discontinuous-lump-like TiC carbide with less than 1 μm on the surface of diamond appeared. There was almost no heat damage in the brazed diamond. The maximal tensile stress in the diamond located at the top reached 60 MPa, while the maximal compressive stress located at the bottom was 120 MPa. As a result, the metallurgical bonding was obtained between filler metal and diamond through the forming the serial of diamond-TiC-filler layer.