Abstract: The additive aluminum is proposed to improve interfacial bonding between Ti-diamond particles and coppermatrix for Ti - diamond/copper composites. The microstructures, thermal properties, interface reaction production and its effect of the different volume fraction of additive aluminum on the properties of the composites are investigated. The results show that the interfacial bonding of the composites could be strengthened by changing the volume fraction of aluminum, which is attributed to forming intermetallic compounds (Al₅CuTi₂ and AlCu₂Ti) on the interface between diamond and copper. At the same time, the relative density of diamond/copper composites is improved. However, thermal conductivity of diamond/Cu composites is reducing with the increase of volume fraction of Al, the formation of intermetallic compounds could hindered the effective interface of heat transfer due to increasing thermal resistance. The volume fraction of diamond and aluminum is designed to 2 vol.% and 75 vol.%, respectively, the highest thermal conductivity of sample reaches to 570 W/(m·K).