In this paper, based on the principle of micro-hot pressing additive manufacturing technology, rapid preparation of graphite silicon carbide ceramic composites is achieved, using natural flake graphite powder as the raw material and thermosetting phenolic resin as the adhesive. Particular focus is placed on the composition of mixed powder, and how this affects its compressive strength and thermal conductivity. The results show that when the natural flake graphite powder and the thermosetting phenolic resin is fixed at 85% and 15%, respectively, the mass fractions of high purity silica powder, short carbon fiber, and intermediate carbon microspheres is 25%, 4% and 21%, respectively. The compressive strength and thermal conductivity of the graphite silicon carbide ceramic composite is 30.82 MPa and 21.65 W/m·K, respectively. By testing the thermal expansion coefficient and oxidation resistance of the composite at 1200 ℃, the oxidation weight loss and the thermal expansion coefficient is determined to be 23.679% and 3.14×10^-6/K, respectively. This composite material is expected to replace graphite casting and be applied in the casting industry.