Abstract: Diamond superhard abrasive tools play an increasingly important role in high-end chips, 3C ceramics processing and other fields. The interface between binder phase and diamond greatly affects the mechanical and wear properties of diamond superhard composites. In order to study the interfacial bonding between binder phase and diamond, Cu₃₅Ni₂₅Co₂₅Cr₁₅ multi-principal components alloy/diamond composite was prepared by spark plasma sintering (SPS). The interfacial reaction between alloy binder phase and diamond particles was studied by thermodynamic calculation and experiments. The results show that chromium reacts with diamond at the interface to form Chromium carbides. Moreover, with the sintering temperature increasing, the thickness of Chromium carbides layer grows and the cohesion coefficient between the alloy binder phase and diamond increases. When sintering temperature reaches 950℃, the Chromium carbides layer is uniform and continuous, and the thickness is about 1.1 μm. The friction and wear tests show that on the surface of the composite sintered at 900℃ and 950℃, the alloy binder phase is removed firstly by the shear stress, and then the diamond particles expose. Due to the retention of the Chromium carbides layer, the grinding performance of the composites is improved effectively. Therefore, appropriate interfacial reaction improves the service properties of the diamond composites.