Abstract: Addressing the current issues of insufficient thermal conductivity and low heat dissipation efficiency in electronic packaging materials, the copper‒diamond composites were prepared with three different methods, namely, traditional powder metallurgy (PM), stirring friction processing (FSP), and spark plasma sintering (SPS), the microstructure, relative density, interfacial state, and thermal conductivity were comparatively analyzed. The results show that the copper‒diamond composites with 50% diamond (volume fraction) prepared by SPS under the sintering pressure of 30 MPa at the holding temperature of 900 ℃ for 20 min have the best performance with the diamond particles uniformly distributed on the copper matrix. The relative density, thermal conductivity, and coefficient of thermal expansion of the SPS composites is 97.4%, 517.04 W·m^‒1·K^‒1, and 6.63×10^‒6 K^‒1, respectively, and there is a transition layer with a thickness of less than 1 μm at the interface, which shows good bonding quality. The performance of the copper‒diamond composites prepared by PM is the second, and that of the composites prepared by FSP is the worst.