Abstract: In this paper,the principle of the fast infiltration in the porous medium of the liquid aluminum alloy is studied,and the calculation model of the anti pressure of the gas inside the mold,which appears in penetration,has been established.This model makes the calculation result even more close to real pouring results.The research shows that anti pressure of the gas is concerned with the permeability of porous medium (the porosity and the hole diameter),the infiltration speed,and the infiltration length.The infiltration process is coupled in simulationg numerically considering the heat exchange between the liquid met al and the particle medium on this foundation.It is proved that the numerical calculations are basically reasonable,and possesses the practical significance to the final optimization of the infiltration technique.