Abstract: A group control system of multi welding power supplies based on DSP was applied to membrane water wall welding machines.The group control strategy of different priorities was introduced to the system, and multi welding power supplies were adjusted in sequence according to this strategy when electric power network parameters changes.Consequently, the shorter time and less error of adjusting were obtained.At the same time, according to the welding area and the temperature field of welding-panel, the real-time adjusting strategy of welding parameters was put forward.On the basis of this strategy, the parameters of multi welding power supplies were adjusted dynamically at different striking places.The experiment results show that using the group control system, the quality of welding seam was improved, and the distortion of welded panel was effectly contralled greatly as well.