Aiming at the problem of accurately calculating the temperature change of gun barrel in the design of gun barrel, a simple algorithm for the heat absorption of gun barrel was proposed. This paper briefly analyzes the energy conversion in gun barrel shooting, verifies it with the gun barrel data of a scientific research product, analyzes the influence of gun barrel heating, and introduces the gun barrel ablation life, the standard of ablation life termination, the cooling measures and the measures to improve the gun barrel life. The experimental results show that the algorithm is feasible and can provide a reference for barrel design.