In order to utilize the latent heat of metal fusion and evaporation, Al20Si/graphite was added into graphite by squeeze casting infiltration. Its ablation properties were tested by oxy-acetylene flame. Compared with graphite, linear ablation rates of Al20Si/graphite decrease nearly by one order of magnitude. However, linear ablation rate of Al20Si/graphite increases with ablation time, which is caused by the change of ablation mechanism. At the beginning of ablation process, thermal chemical erosion plays an important part and thermal protective effect comes from the melting of Al20Si, the alleviation of liquid Al2O3 towards flame scouring and the decrease of porosities compared with graphite, while with ablation processing thermal mechanical erosion turns to dominate and thermal protective effect is mainly presented on the prevention of oxygen diffusion by the molten Al4SiC4 covered on ablation surface and the oxygen diffusion barrier effect of Al4SiC4 stuffed into graphite pores.