Abstract: High volume fraction Cu/diamond composites were successfully prepared by spark plasma sintering (SPS). Their relative density, thermal conductivity and coefficient of thermal expansion (CTE) were investigated. It is found that the composites have a uniform microstructure, with the relative density from 94% to 99%, the highest thermal conductivity of 305 W· (m·K)^-1, and the CTE matching with common electronic semiconductor materials. All these properties can meet the demands of electronic packaging materials.