This paper presents the influence of the weld widthroot gapand weld offset of the T-joint to the overall stiffness of sandwich plate with finite element simulations. From the results of finite element calculation and some of experimental verification we can see:(1) For this structure, welding joint damage occurs before the face plate buckling.(2) Among the factors weld widthgap and weld offset of the T-joint, the weld width affect the overall stiffness the most. (3) When root gap and weld offset lower 0.1mm and 0.12 mm, respectively, they have a little influence on the resistance of deformation ability for the sandwich plate, they can be ignore.