Abstract: The welding deformation of large steel deck blocks is studied by the thermal elastic plastic finite element method. The change of the structure and stress field can be obtained based on the 3D Shell element and the double ellipsoid heat source model, and then the welding deformation of large steel deck blocks and the residual stress distribution can be acquired. The influences of different welding sequences and fixture arrangements of the deck bocks on the residual stress and the welding deformation are studied. The results show that the deformation caused by the symmetry alternant welding method is the smallest. The welding deformation and the amount of work are both small when putting battens to the edge and center of the deck block. By optimizing the welding sequence and fixture arrangement, the welding of the large steel deck can be accurately controlled.