Abstract: An appropriately structured gradient coating on the surface of C/C composites, consisting of, from inner to outer, a SiC transiting layer, a SiC compacting layer, a MoSi2/SiC double phase layer and a MoSi2containing outer layer, was prepared by a twostage coating method. As the holding time at high temperature stage is increased, the MoSi2 outer layer becomes more continuous. The adhesion between the coating and the composites is mainly caused by a metallurgical bond and a mechanical bond．The surface of the coating is sealed by Si(OC2H5)4, and SiO2 gel fills the cracks in the coating and covers it. Oxidation of the specimen with an unsealed coating causes mass loss, while the specimen with the sealed coating shows a mass gain in air at 1500℃.