Abstract: Because the stiffness of extra thin-plate welded joint or structure is very small, welding distortion is apt to generate after welding. Therefore, it is very meaningful to predict welding-induced deformation accurately in such welded joint. Inherent strain method is a practical approach which can be used to predict welding deformation in large and complex structures. However, this method is seldom employed to estimate welding deformation in extra thin-plate joints. In this study, the features of inherent strain distribution in bead-on joint with 1 mm thickness was investigated by means of thermal elastic plastic finite element (T-E-P FE) models. Meanwhile, the influence of weld length on the distribution of inherent strain was also clarified. Moreover, the welding deformation in extra thin-plate joints with different weld lengths was calculated by using inherent strain method. The comparison between the results obtained by inherent strain method and those computed by T-E-P FE models shows that when the weld length is up to a critical value, the inherent strain method can be used to predict welding deformation in the extra thin-plate joints.