This study investigated the simplified crack growth analysis method for side-shell-plate to annular-bottom-plate welded joints in cylindrical tank under cyclic large deformation. Under cyclic large deformation, gross plasticity behavior is occurred in crack section with high crack growth rate of ultra low cycle fatigue fracture mode. For the crack located in shell-annular welded joints, there are not sufficient solutions to calculate nonlinear fracture mechanics parameters to estimate this high crack growth rate, such as J-integral, crack mouth opening displacement and load point displacement. Predicted equations using fully plastic solutions determined by series FE-analyses have been developed to simplify crack growth analyses. And ultra low cycle fatigue crack growth tests have been conducted with structural model of L-type shell-annular welded joints. It has been concluded that simplified crack growth analysis method has good predictability for fracture behavior of the structural model.