Abstract:         In this paper, the finite element analysis software ABAQUS was used to conduct finite element simulation of laser welding, MAG welding and laser-MAG arc composite welding under the same conditions. By comparing the changes of temperature field and post-welding stress field among the three, the interaction between laser and MAG arc in the composite welding process was analyzed. It can be seen from the analysis that laser-MAG arc composite welding combines the advantages of MAG welding width and laser welding depth, and further increases the size of the weld pool, fully heats the welded sheet, and reduces the cooling rate after welding. When the power of laser or MAG arc changes, the surface size of molten pool changes with it. The root size of molten pool is greatly affected by the change of laser power, but the power change of MAG arc has little influence on it. The MAG arc has a certain after-heat effect on the laser weld, reducing the cooling speed of the laser weld, effectively solving the problem of laser welding energy concentration, small heat input, and fast cooling speed caused by large high stress area. The stress distribution of the weld is uniform, the residual stress value is reduced, and the reliability and fatigue resistance of the weld joint are improved.