polycrystalline cubic boron nitride has attracted attention because of its excellent mechanical properties and physical and chemical stability, which has a wide application prospect in the field of machining. In this paper, Al, Co, W, TiN and cBN powder were mixed by ball milling, and then sintered with WC-Co cemented carbide substrates with different Co contents at 1500℃ and 5.5 GPa by high temperature and high pressure sintering method. The influence of different alloy substrates on the interfacial strength of PcBN composite and mechanism were systematically studied. When the cemented carbide is WC-11.5%Co, the combined effects of bending strength and Vickers hardness of PcBN composite are 1623.67 MPa and 46.03 GPa. By microstructure analysis, the combination between cBN phase and WC-Co alloy substrate mainly depends on the mutual penetration and diffusion of Co atoms under the conditions of high temperature and high pressure. The Co atoms diffuse and pin from the WC-Co alloy substrate with high concentration to the cBN phase with low concentration, and finally the interface is bonding. Through heat treatment, the material is physically damaged on the surface, which is mainly manifested by the precipitation of binder phase from the surface of the sample. At the same time, the surface of the sample is oxidized to form oxidation phases such as B₂O₃, Al₂O₃ and TiO₂.