A thermal stability of carbon-carbon composites with increase of oxidation resistant filler, MoSi2, have been studied by thermogravimetric analysis during the graphitization process. In this work, the initial decomposition temperature, temperature of maximum rate of weight loss, integral procedure decomposition temperature, and decomposition temperature range for the degradation temperatures, and the activation energy based on Horowitz-Metzger calculating method were characterized in a thermal stability study. It has been found that 12-20 wt% filler on the basis of the resin matrix leads to an improvement of degradation temperature and to an effectively increase of activation energy of the composites. This is probably due to the effect of the inherent MoSi2 properties, resulted from a brittle-to-ductile transition for increasing the interfacial adhesion between fiber and matrix, and a mobile diffusion barrier formation against oxygen attack, in the vicinity of 900-1000 degrees C.