Abstract: Based on the pooling inversion method, the heat source model and related parameters matched with the engineering practice were obtained. Birth and death technique of the nonlinear MSC was employed. Marc software was adopted to simulate the GMAW multi-pass welding of X80 pipeline steel with U-V composite groove. Further analysis was carried out to demonstrate the residual stress of the welded joints with the reinforcement and the non-reinforcement. The results showed that both of longitudinal residual stress and transverse residual stress had a “double peak” phenomenon, which was concentrated at the weld toe. The longitudinal and transverse peak stresses were higher than those of the joint with the non-reinforcement, exceeding the base metal yield strength of X80 pipeline.