Fatigue crack propagation behaviors of the as-prepared and thermally exposed (700 degrees C/196h, 800 degrees C/196h) C/Mo double-coated SiC fiber-reinforced Ti6Al4V composites were investigated. The results show that interfacial microstructure evolution has significant effect on fatigue crack propagation behaviors. As for the as-prepared and 700 degrees C/196-h thermally exposed composites, fiber-bridging accompanied with interfacial debonding can decrease the crack growth rate significantly, while the latter one has lower crack growth rate at the early fatigue crack propagation stage, as the diffusion of Mo atoms makes the matrix close to the interface have more ductile beta-Ti. However, fiber-bridging phenomena disappeared with the altered interface in the composite after 800 degrees C/196-h thermal exposure. Fatigue fracture analysis further reveals that multistep deflections of crack in interface contribute to the improvement of interface toughness. The formation of ductile beta-Ti layer resulted from the diffusion of Mo atoms is beneficial to blunt the crack tip.