Abstract: The thermal shock fatigue character of cermets has been studied and the formative mechanism of crack discussed in detail. The results have shown that the incubation period of crack nucleation decreases and the propagation rate of crack increases with increasing the cyclic temperature. The propagation rate of crack also decreases with increasing the binder content of cermets. The crack formation of thermal shock fatigue is related to the nucleation, growth and join of microvoid. The SEM has also denoted that there are some fatigue striae on the fracture surfaces.