To improve the service life of hot forging die for 5CrNiMo steel, a shot peening strengthening process was proposed. Firstly, through the simulation model and experimental verification of shot peening process, the optimal shot peening process parameters were obtained to be the steel ball diameter  of 0.6 mm, the initial speed of 75 m·s-1 and the coverage rate of 150%, and the influences of parameters on the residual compressive stress distribution were analyzed. Secondly, the samples of 5CrNiMo steel without shot peening and with shot peening under the best process parameters were compared and analyzed. The results show that the surface hardness of samples increases by about 10% after shot peening. Compared with the sample without shot peening, the friction coefficient of the sample with shot peening decreases significantly, and the wear resistance is significantly improved. This is because the large amount of graphite adsorbed by the dent forms a graphite isolation layer, which reduces the direct contact area of  metal surfaces. Finally, the optimal shot peening process was applied to the production of an automobile crankshaft final forging die. Production verification shows that there are a large number of collapse, fatigue cracks and excessive wear on the surface of the mold without shot peening treatment after 6000 pieces of service, while these defects do not appear on the surface of the mold after shot peening, and its service life is increased by about 50%.