Abstract: Light weight thermal insulation materials have been widely used in the thermal protection system of aircraft power plant, but the existing technology is difficult to achieve the synergy of many technical goals such as high load, light weight and thermal insulation. In this paper, a kind of lightweight, high strength and low thermal conductivity silicon carbide/graphite composite was rapidly prepared based on the principle of micro-hot pressing additive manufacturing and forming technology. The variation law of compressive strength and thermal conductivity of composite materials under different forming densities was studied. By changing the material formula composition (including thermosetting phenolic resin powder, high purity silicon powder and expandable graphite, etc.), the compressive strength and thermal conductivity of composite materials were adjusted forward and backward, and its internal mechanism was revealed. This research finds that when the mass fraction of phenolic resin powder, high purity silicon powder and expandable graphite is 30wt%, 30wt% and 2wt%, respectively, the silicon carbide/graphite thermal insulation composite has the properties of low density (<1.2 g/cm³), high compressive strength (>15 MPa) and low thermal conductivity (< 1 W/(m·K)), which has a good application prospect in aerospace.