Abstract: The 63vol% Diamond/Cu-Ti composites were prepared by vacuum hot pressing. The influence of minor Ti addition on the interfacial microstructure and thermal conductivity of Diamond/Cu-Ti composites was studied. The thermal conductivity of Diamond/Cu-Ti composites first increases and then decreases with increasing Ti contents. The maximum value of 511 W/(m·K) is obtained at 1.1wt%Ti. When Ti contents are less than 1.1wt%, the number and area of carbides generated during the sintering process increase with the increase of Ti content, the interface bonding is optimized, the interface bonding strength is improved, the number of interface heat transfer channels is increased and the thermal conductivity of Diamond/Cu-Ti composites is improved. The increase of Ti content is accompanied by the increase of carbide thermal resistance and the deterioration of the thermal conductivity of the matrix. The excess Ti element increases the thickness of the carbide layer with low thermal conductivity, increases the thermal resistance of the carbide layer itself, reduces the interfacial thermal conductivity, and decreases the thermal conductivity of the Diamond/Cu-Ti composites.