Shot peening can improve fatigue strength of materials by creating compressive residual stress field in their surface layers, and offers a protection against crack initiation and propagation, corrosion, etc. And fatigue fracture and stress corrosion cracking of NAK80 steel parts are improved effectively. Currently there lacks in-depth research in which the beneficial effect of the residual stress may be offset by the surface damage associated with shot peening, especially in terms of the research on the effective control of shot peening intensity. In order to obtain the surface residual stress field of NAK80 steel after shot peening, the samples are shot peened by pneumatic shot peening machine with different rules. The residual stress in the precipitation-hardening layer of NAK80 steel is measured before and after a shot peening treatment by X-ray diffraction method. In order to obtain true residual, stress field, integral compensation method is used to correct results. By setting up analytical model of the residual stress in the process of shot peening, the surface residual stress is calculated after shot peening, and mentioning the reason of errors occurred between calculated and experimental residual stresses, which is mainly caused by the measurement error of the shoot arc height. At the same time, micro hardness, microstructure and roughness in the precipitation-hardening layer of NAK80 steel before and after shot peening were measured and surveyed in order to obtain the relation between shot peening strength and surface quality in the precipitation-hardening layer. The results show that the surface quality of NAK80 steel is significantly improved by shot peening process. The over peening effect is produced when the shot peening intensity is too high, it is disadvantageous to improve sample's surface integrity, and leading to reduce the fatigue life. When arc high value of optimal shot peening is 0.40 mm, the surface quality is the best, and. the depth of residual stress in the precipitation-hardening layer reaches to about 450 pm. Numerical calculation is very useful to define the process parameters when a specific residual stress profile is intended, either to quantify the benefits on a specific property like fatigue life or to help on modeling a forming process like shot peen forming. In particular, the proposed parameter optimization in the progress of shot peening and effective control of the surface texture provide new rules for the quantitative evaluations of shot peening surface modification of NAK80 steel.