Abstract: The welding of the boss and thin plate GH4169 alloy is carried out by electron beam welding. The influence of heat input,plate thickness,and number of boss on the deformation of weldments are investigated. The results show that weldments of the plate and the boss have an in-plane shrinkage deformation and out-of-plane buckling deformation after welding. The shrinkage deformation of weldments along the plate edge is large in the middle,while it is small on both sides,and that the middle concave degree increases with the increase of heat input. Moreover,the amount of shrinkage deformation is proportional to the heat input,and inversely proportional to the thickness of the plate. When the heat input increases from 54 J/mm to 84 J/mm during welding single boss with 2 mm thick thin plate,the shrinkage deformation increases from0. 20 mm to 0. 48 mm. While the heat input is 54 J/mm and the thickness of the plate is 2 mm,the shrinkage deformation is 0. 20 mm,and it becomes almost non-deformed when the thickness of the plate is 5 mm. The buckling deformation of single boss weldments is that the edge of weldments irregularly warps up and down around the circular weld,which is mainly caused by the angular deformation of the weld. The buckling deformation of double-boss weldments presents wave-like deformation,which changes alternately from upwarp to downwarp,and it is caused by angular and deflection deformation. The thinner the plate is and the greater the heat input is,the larger the deformation of the upwarp and downwarp is. The buckling deformation of the welded double boss is greater than that of the welded single boss.