Abstract: Diamond/Al composites were fabricated by spark plasma sintering（SPS）. The thermal conductivity of the samples with different particle volumes and particle sizes was investigated，and the influence of the processing parameters on the thermal conductivity of the composites was also considered. The results show that diamond/Al composites with good thermal conductivity can be made by SPS，and the density is the most important factor which affects the thermal conductivity of the composites. The diamond/Al composite with the highest thermal conductivity can be obtained when the composite contains  50 vol% diamond particles of 70 μm sintered at 550℃，and its thermal conductivity is 182 W/(m·K)，which is 34.8% higher than that of the sample of the pure Al sintered under the same condition，showing that the diamond particle gives significant improvement of the thermal conductivity of Al matrix composites.