Abstract: According to the theories of coating shear failure mechanism and fatigue cumulative damage, a life prediction model of gun barrel was proposed based on the shear fatigue damage accumulation at the interface of coating and substrate in barrel. The interface shear stress of a small caliber gun barrel during a cooling cycle was calculated, then the fatigue life was predicted respectively for three barrels with different substrate materials, and the influence of high-temperature strength of substrate steel on barrel life was studied. The research results show that the high-temperature strength of substrate is a key factor which concerns barrel life, and the interface tensile strength decline caused by temperature rise is a significant inducement of coating failure and the end of barrel life. The increase of room-temperature strength of substrate is of little help to barrel life improvement, but the increase of high-temperature strength of substrate can observably enhance barrel life. The comparison of life test results and the prediction results verify the availability of life prediction model and the validity of prediction results.