Aiming at the problem on the life prediction of gun barrel, this paper discusses its life prediction theoretical method of gun barrel. Describes the process of reducing and characteristics of the barrel life and analyzes 3 factors that affect it, including fatigue life, erosive abrasion life and the impact of the barrel by temperature and gas. The paper summarizes the theoretical methods of gun barrel life prediction. The analysis results show that prediction results are accurate and have some reference value for life prediction of gun barrel.