Abstract: The typical Q345 steel cruciform welded joint on ship was treated by shot peening under different shot peening intensities (0.167, 0.183, 0.198 mmA). The surface and depth distribution of residual stress and fatigue life of joint after shot peening were studied, and the optimal shot peening process was obtained. The results show that after shot peening, the residual tensile stress on the surface of the welded joint was eliminated, the high level of residual compressive stress was introduced, the distribution uniformity of the surface residual stress was improved, the depth of the residual stress affected layer was increased, and the fatigue life was prolonged. With the increase of shot peening intensity, the introduced residual compressive stress increased, the distribution uniformity first increased and then decreased, the depth of the residual stress affected layer increased, and the fatigue life first prolonged and then was shortened. The optimal shot peening intensity was 0.183 mmA. Under this intensity the residual compressive stress on the welded joint surface was large, the distribution uniformity was the best, the depth of the residual stress affected layer was large, and the fatigue life was the longest.