Thermal stability of SiC_f/Ti-60 composites under thermal exposure at different temperature was studied. Interfacial reaction layer and element diffusion of SiC_f/Ti-60 composites after HIP and thermal exposure were also investigated. The results showed that the mainly product of reaction layer was TiC. The interdiffusion of C or Si in SiC fiber and Ti or other elements in matrix occurred. TiC was formed at the interface and in the matrix due to the high diffusion rate of C. TiC mainly existed on the grain boundaries of matrix. The growth behavior of SiC_f/Ti-60 composites reaction layer was influenced by diffusion and followed an Arrhenius law. The preexponential factor and the activation energy of SiC_f/Ti-60 composites were 2.27×10_-4 m/s_1/2 and 118 kJ/mol respectively.