Aiming at predicting the temperature and deformation of automatic rifle’s barrel in successive firing process, a thermal-elastic coupling axial symmetry finite element model was established. Compared with the experiment results, the correctness of the model was verified. The temperature and deformation situation of gun barrel during 150 successive firing processes were calculated. Analyze the influence of barrel wall thickness and firing frequency on barrel transient temperature and deformation. The calculation results show that the barrel wall thickness of small caliber automatic rifle increased, less residue temperature and deformation of gun barrel after 150 successive shooting decreased. When firing rate decreases 15%, residue temperature and deformation of gun barrel have not change.