Abstract: The new generation of Al/diamond composites has been more and more used in high power integrated circuit packaging materials because of its high thermal conductivity and low thermal expansion coefficient. At present, the main methods of preparing Al/diamond composites are powder metallurgy, hot isostatic pressing, plasma sintering, stirring melting and casting, non-pressure infiltration and pressure casting, etc., but the large-scale industrial production has not been effectively realized in China.Based on the principle of pressure casting method, a new process of Al/diamond composites prepared by molten high pressure die casting was proposed.The results show that the process can meet the requirements of batch production.The volume fraction of diamond is stable at 65vol%-68vol%.The composites with denser structure and more uniform structure can be prepared, and the thermal conductivity is as high as 580 W/ (m·K).Due to the reduction of diamond preform preparation process, compared with the previous production process, the efficiencyis improved and the production cost is reduced.