A new method was proposed to fabricate diamond/Cu composites. Double-layer diamond particles were directly compressed at ultra-high pressure to prepare the preform and then sintered in a vacuum equipment for densification. The raw diamond particles were coated with zirconium carbide by magnetron sputtering for the inner layer and then deposited with copper by chemical method for the outer layer. Prepared with these particles, the composites had good interface bonding and homogeneously distributed particles in the copper matrix. The thermal conductivity of 65 vol% diamond/Cu composite was as high as 720 W m(-1) K-1. When the diamond content increased to 70 vol%, the coefficient of thermal expansion was extremely low (4.33 x 10(-6)/K). With superb thermal-physical performance, diamond/Cu composites are potentially applicable to electronic packaging.