Abstract: Diffusion bonding of ceramic matrix composite TiC-Al₂O₃ and tool steel W18Cr4V was successfully carried out by addition of composite interlayer Ti Cu Ti at 1130℃ for 1 h with a pressure of 15 MPa.Shear strength of the bonded TiC-Al₂O₃ W18Cr4V joint is 103 MPa. Microstructure characteristics and microhardness in the diffusion bonded TiC-Al₂O₃ W18Cr4V joint were investigated by means of scanning electron microscope, X-ray diffractometry and electron probe microanalysis.The results indicate that Ti Cu Ti interlayer has been fully diffused to combine with matrixes including TiC-Al₂O₃ and W18Cr4V and a diffusion transition zone with a thickness of 90μm is formed.The microhardness from TiC-Al₂O₃ to W18Cr4V across the diffusion transition zone decreases from 3400 HM to 1000 HM. The phases formed in the diffusion transition zone are Ti₃Al, CuTi₂, Cu and TiC.