Abstract: Effects of heat source offset distance from steel and aluminum interface (heat source offset distance) on the welding temperature field and residual stress of plasma arc welded joint of steel/aluminum dissimilar materials were studied by finite element simulation and verified by experiments. The results show that the temperature field of the welded joint of steel/aluminum dissimilar materials was asymmetrically distributed, and the temperature gradient on the steel side was lower than that on the aluminum side. With increasing heat source offset distance, the temperature and fusion width on the steel side of the joint increased, and those on the aluminum side had the opposite trend. The residual stress on the aluminum side of the joint was mainly tensile stress. On the steel side, the residual tensile stress near the interface decreased with increasing heat source offset distance, and finally changed into compressive stress; the residual stress far away from the interface was mainly compressive stress. The relative error between the experimental residual stress and the simulation was lower than 8%, and the residual stress situation was in line with the simulation.