Abstract: The thin-walled plate dryer is a key component of new energy efficient conduction drying equipment, and has 180 welds between the punching board and the upper cover. The above factors cause the welding process of plate dryer is very complex, so the numerical simulation method by using segmented moving heat source was adopted. The results show that the maximum residual stress of upper cover is 233 MPa which is in the initial weld. The welding deformation of workpiece is bulging upward along the center, the amount of deformation gradually increases from outside to inside diameter, the maximum deformation is 22.8 mm which is in the inside diameter. A small amount of flexure deformation occurs in the workpiece, whose welding direction contraction is 3.61 mm, and vertical welding direction elongations are 1.81 and 1.69 mm to the opposite ends respectively. The deformation distribution of numerical simulation is in a good agreement with actual welding.