The whole process of the relief of the welding residual stress through an explosive treatment is simulated by using the nonlinear
dynamic finite element method. First, the cooling process of a butt-welded steel plate after welding is simulated and the generation of residual stress in this course is calculated by using the indirect iteration method of coupled temperature field and stress field. When the high temperature of the weld joint drops down to the chamber temperature, asymmetric residual plastic stress and strain are aroused since the deformations are restricted by the surrounding area. Then, a movable explosive loading is applied to the weld line to simulate the blast of a strip of detonator laying on it. In this way, the variation of the residual stress in the whole plate is analyzed numerically. The numerical results indicate that the explosive treatment can lead to a redistribution of the welding residual stress, which relieve the large residual stress effectively. The explosive method is an economic and efficient way to reduce the residual stress in large-sized structures. This research supplies a powerful tool for the investigation of the mechanism of the explosive treatment.