Abstract: In order to investigate the residual stress and deformation of dissimilar steel welded joints under different welding processes, finite element simulation analysis is carried out for two schemes: conventional welding and composite welding. The simulation results indicate that, for conventional welding, the peak tensile stress near the Q460 fusion line is 54.9 MPa, the maximum stress near the Q235 fusion line is 38.0 MPa, and the compressive stress at the weld center reaches 174.1 MPa. For composite welding, the peak tensile stress near the Q460 fusion line is 101.7 MPa, the maximum stress near the Q235 fusion line is 50.3 MPa, and the compressive stress at the weld center is 145.2 MPa. In the conventional welded joint, longitudinal tensile stress exists within the weld zone, while compressive stress appears in regions away from the weld. In the composite welded joint, obvious compressive stress occurs inside the weld zone, longitudinal tensile stress arises outside the weld, and compressive stress is distributed on both sides of the heat-affected zone. The maximum deformation of conventional welding and composite welding is 1.61 mm and 2.01 mm, respectively. On this basis, welding process parameters are optimized, and the optimal parameter combination for minimizing residual stress is determined. The results reveal that proper selection of buffer layer materials can improve residual stress distribution characteristics, which provides an important reference for research on fatigue failure induced by residual stress in dissimilar steel welded structures.