Abstract: As a mechanical strengthening process of 8Cr4Mo4V steel, shot peening can form a residual compressive stress layer of nearly 300 μm on the surface of the material, which is beneficial to improve the contact fatigue performance of the material. Due to the large roughness of the near-surface layer of the material after shot peening and the existence of cracked carbides, the grinding treatment is required. The additional stress introduced by the grinding process has a great influence on the stress distribution after shot peening.The influence of shot peening and grinding process on the surface structure and residual stress distribution of 8Cr4Mo4V steel was explored by SEM, XRD, residual stress test and other methods. The results show that with the increase of the peening strength, the distribution of the residual stress deepens, and the highest depth of the stress-affected layer reaches about 320 μm.Due to the high stress and high density of dislocations on the surface of the material after shot peening, the martensitic diffraction peaks have a left-shifted peak position, an increase in the full width at half maximum, and a decrease in strength.Based on the method of calculating the dislocation density with the WH theory, the relationship between the dislocation density distribution and residual stress distribution in the surface layer is given.