Abstract: A thermo-mechanical coupling finite element model of butt multi-pass welded steel plate was established, and the transverse residual stresses during the multi-pass welding process were simulated numerically by the thermo-elastoplastic method. The simulation results were validated experimentally through the corrosion layer removal method combined with the magnetic anisotropy technique. The distribution of residual stresses inside the steel plate at different welding stages was simulated by the establisheded model. The results show that the simulated transverse residual stresses agreed well with the test results, with an average relative error of 8.73%, confirming the accuracy of the developed model. The simulation results further revealed that the peak residual stresses occurred not only on the plate surface but also exhibited a significant distribution within the subsurface layer up to a depth of 3 mm. As the number of weld passes increased, the peak residual stress inside the plate decreased after each pass, and after complete cooling, the peak tensile stress showed a partial recovery in localized areas. The transverse residual stress exhibited a “W”-shaped distribution along the path perpendicular to the weld seam, and along the path parallel to the weld seam, it showed a higher magnitude in the middle section and lower values near both ends. The transverse residual stress decreased with the increase of depth, and transitioned from tensile to compressive stress at approximately 7 mm below the surface.