Abstract: The welded joints of ducts often generate harmful residual tensile stresses at the weld seam, significantly reducing the fatigue life of the duct welds. To improve the fatigue life of the welded joints, dynamic impact methods are generally employed to modify the surface of the weld zone, adjusting the magnitude and distribution of residual stresses. The residual stress distribution in the welding area of a duct at the outlet of a rocket engine kerosene stage 1 pump was investigated. A double-ellipsoid heat source model was used to simulate the welding heat input, and the birth-and-death element method was employed to simulate the formation of the weld seam. The residual stress distribution in the welding zone was then obtained. Subsequently, laser shock peening was applied to the surface of the welding zone for surface enhancement.Finite element numerical simulations were performed to study the residual stress and deformation of the welded duct before and after laser shock peening. The results show that after laser shock peening, the residual tensile stress in most areas of the duct surface is significantly reduced, and some local areas even exhibit beneficial compressive residual stresses. This has the potential to significantly improve the fatigue life of the welded joint of the duct.