Abstract: The sandwich composite structure of "Al/Si-Al/Diamond-Al/Si" was prepared by pressure immersion method to test its heat conduction properties. Firstly, the aluminum alloy ingot was melted, and the quality of the molten aluminum was tested to determine the appropriate refining process and moment of infiltration. A high pressure of 80 MPa was applied to the refined aluminum alloy liquid to fully infiltrate the silicon preforms powder to obtain Al/Si composite materials, and the thermal performance was also tested. The results show that the larger the silicon particle size and the lower the volume fraction, the higher the thermal conductivity of the Al/Si composite. The smaller the silicon particle size and the higher the volume fraction, the lower the thermal expansion coefficient of the composite. Based on the above results, the "Si-Diamond-Si" prefabricated block structures are determined, and then "Al/Si-Al/Diamond-Al/Si" sandwich composite structures are prepared at one time by the pressure infiltration method. The thermal conductivity of the sandwich composite structure containing the optimal silicon particle size and volume fraction is between 450 W/（m·K） and 500 W/（m·K）, which are higher than those of Al/Si composite materials and pure metals such as aluminum.