Abstract: To address the bottleneck in thermal dissipation capacity of traditional aluminum alloy heat sinks, a sandwich-structured graphite-aluminum composite is proposed in this paper. Comparative experiments demonstrate its superior lateral heat dissipation to aluminum alloys. Based on the established simulation model, a semi-physical calibration method is employed to quantify both in-plane and through-plane thermal conductivities of the graphite layer and composite. The results reveal that the graphite-aluminum composite with in-plane thermal conductivity of 390 W/(m·K) has copper-equivalent heat dissipation performance and its density is much lower than that of copper, demonstrating substantial advantages for aerospace lightweight engineering. The quantified thermal parameters enable thermal designers to efficiently develop optimized heat dissipation solutions through simulation-driven design iterations.