Abstract: Diamond/copper composites have the excellent thermal conductivity and the controllable thermal expansion coefficient, making them expected to become new generation of thermal management materials. However, the wettability between diamond and copper is poor, and the interface bonding of the prepared composites is poor, resulting in the large thermal resistance between the interfaces and affecting the thermal conductivity of the composites. Improving the sintering method or modifying the interface can address the issue of poor interfacial bonding and enhance the thermal conductivity of the composites. The commonly used preparation methods of the diamond/copper composites were summarized and the interface modification were introduced, including surface metallization of diamond and alloying of copper matrix, whose principle was element addition at the interface between diamond and copper to form the corresponding carbide layers, thereby improving the diamond/copper interface bonding and enhancing the thermal conductivity of the composites. The commonly used elements in interface modification were W, Mo, Cr, Ti, Zr, and B, which could effectively improve the interface bonding and increase the thermal conductivity to over 900 W·m⁻¹·K⁻¹ at the highest. The application of first-principles calculations in diamond/copper composites was also introduced to study the mechanism of interface improvement and predict the influence of interface modification elements, providing the theoretical guidance and reducing the research costs. Finally, the research direction of the diamond/copper composites weas prospected.