In this study, the welding stress of in-service welding on the X80 steel pipeline was investigated using the 3D finite element method. The parameters of heat source and axial and hoop welding stress were verified in the experiment. As shown in the results, in the heat-affected-zone (HAZ) location of the pipeline and sleeve, the outer wall was predominantly under compressive stress, while the inner wall was mainly subjected to tensile stress. The hoop stress (