Abstract: Graphite/aluminum composites have important applications in rail transportation and other fields because of the unique high-temperature stability. Due to the difference in physical properties of graphite and aluminum melt, the high gas pressure environment is required to drive the aluminum melt into the porosity of graphite matrix to improve the mechanical strength and electrical conductivity of the composite. The infiltration dynamics of aluminum melt, which highly depends on the interfacial wettability between graphite phase and aluminum phase, will has a significant effect on the final composite's performance. Consequently, on the basis of experiments and numerical simulations, we studied the effect of silicon volume fraction on the infiltration dynamics of aluminum melt into the porous graphite matrix. Results show that adding silicon will effectively promote the infiltration of aluminum-silicon (Al-Si) alloy melt, achieving a higher filling rate with a shorter filling time. However, the promotion effects of adding silicon will come to its limit due to the effects of local pore residual gas. Meanwhile, the pressure and velocity fields during the infiltration of Al-Si alloy melt in a porous graphite structure are described in detail and the conductivity of the composites is discussed.