There are two ways of conventional thermal distortion analysis. One is thermal elastoplastic analysis and the other is equivalent forces method based on inherent strain. The former needs exorbitant analysis time, while the latter cannot obtain stress results and requires more time with loads modeling on curved plates. To solve those time-consuming problems, a new kind of thermal distortion analysis method was developed. In this method, inherent strains are devised to be used as direct input factors as boundary conditions. Suggested analysis method was already adopted at welding distortion analysis of large hull block, which was considered as impossible.