Abstract: The high temperature inoxidizable behavior of SiC/MoSi₂ and SiC/Mo (Si, Al)₂ prepared by the infilt ration method was studied, and the shape and mass increase induced by oxidate process were discussed in the paper. The results show that the composites will be inactive after high temperature oxidation for 3 h, and the“Pest” phenomenon will disappear when the composites continue to oxide at 500℃. The oxide mass gain of SiC/Mo(Si, Al)₂ is bigger than that of SiC/MoSi₂. When SiC reinforcement is in-situ formed in SiC/MoSi₂ composite, the ability of inoxidation is bet ter because of the higher interface binding force.