Abstract: Shot peening, pre-fatigue and re-shot peenting were conducted on annealed Q345B steel in turn, and the effect of re-shot peening on the residual stress and fatigue life was studied by X-ray/stripping method. With the residual stress after pre-fatigue as the initial stress, the random projectile re-shot peening finite element model was constructed. The influence of coverage rates (100%, 200%, 300%), the projectile diameters (0.4, 0.5, 0.6, 0.7 mm) and projectile initial velocities (25, 35, 40, 45 m · s ⁻¹) on the residual stress distribution and the affected layer depth and the surface roughness of the sample were studied. The results show that re-shot peening could restore the residual stress relaxed by pre-fatigue treatment to the level after single shot peening, and further prolong the fatigue life. The simulation results show that with the increase of coverage rate, the residual compressive stress and the affected layer depth had no obvious change, and the surface roughness of the sample increased. With the increase of projectile diameter and initial velocity, the residual compressive stress and the affected layer depth both increased first and then became stable, and the surface roughness increased. The optimal shot peening parameters were as follows: the projectile initial velocity of 40 m · s ⁻¹, the projectile diameter of 0.6 mm and the coverage rate of 100%. At this time, the residual compressive stress and the affected layer depth of the re-shot peening sample were large, and the surface roughness was small, and the comprehensive reinforcement effect was the best.