The oil and gas transported by subsea pipelines contains a large amount of corrosive media. Bimetallic composite pipes, with advantages such as high load-bearing efficiency and strong corrosion resistance, are gradually being applied in the field of offshore oil and gas transportation. To enhance the authenticity and reliability of simulation calculations, samples were taken from the composite pipe in this study. The interface size was determined through experiments, and then a finite element model for welding of bimetallic composite pipes with a metallurgical interface was established. The dynamic process of pipeline welding was simulated using the DFLUX subroutine and element birth and death technique. The distribution of welding residual stress was analyzed by adopting the thermal-mechanical coupling method, and the influence of welding residual stress on the ultimate bearing capacity of the pipeline was studied.The results show that: welding residual stress changes the dangerous location under the ultimate bending moment and decreases the ultimate bending moment by 20%; however, it has little influence on the ultimate internal pressure and ultimate tensile force of the bimetallic composite pipe. Welding residual stress increases with the increase of welding heat input and decreases with the increase of welding layers. Nevertheless, when the number of welding layers is relatively large, remelting occurs at the weld, which leads to a rebound of welding residual stress and an increase in the fluctuation of stress distribution.