The hindrance which currently precludes the use of Cf/SiC composites is the oxidation of carbon fiber at the temperature higher than 400℃.Therefore,it is necessary to develop coatings capable of protecting Cf/SiC components from oxidation.This coatings consist of three layers,a CVD-SiC bonding layer,a self-sealing active layer by forming glassy phases on exposure to oxygen,and a CVD-SiC erosion resistant layer.Oxidation tests was carried out.The results indicated that the samples with only CVD-SiC coating have much mass loss,and the samples with three layers of coatings including a self-sealing active layer have little mass loss from the temperature of 800℃ to 1200℃.Samples with self-sealing active layer which underwent an oxidation test at 1000℃ in the atmosphere for 288hr suffered only 2.3% mass loss and a residual strength of 452.9MPa.At the same time,CVD-SiC shows various appearance after oxidation at 800℃,1000℃,and 1200℃.The surface formed at 1200℃ has some liquid phase characteristics.