Creep deformation is of vital importance on the thin-walled tube structure under external loadings, such as in-service cladding tubes. To improve the efficiency and accuracy of the creep deformation computation of the cladding tube, a novel continuum-based degenerated 5 degree of freedom (DOF) shell element is developed based on the continuum mechanics and finite element method. The degenerated shell element is implanted in the self-developed software BINE 2.0. The results of BINE 2.0 showed well agreement with commercial finite element software ABAQUS and analytical results. The ovality of the cladding middle section increases slowly at the beginning of the life and increases fast at the end of life until collapse due to the thermal and irradiation creep effect. The continuum-based shell element can be applied to the creep analysis of the cladding tubes of the nuclear reactor.