Abstract: This paper is to discuss the strengthen methods which can effectively increase the critical pressure of instability with the unusual features and usual features of ring-stiffened cylindrical shells. For the structure with usual features, non-uniform stiffeners are used to increase the critical pressure for instability. Furthermore，the theoretical method and finite element method are applied to analyze the critical buckling pressure of a submarine cabin. The comparison results showed that the strength method of non-uniform stiffeners can effectively improve the critical pressure of ring-stiffened cylindrical shells, while the combine strength method with longitudinal and circumferential stiffeners was validated to effectively increase the stability of a ring-stiffened cylindrical shell with unusual features.