Generally, we increase the cross sectional area of circular transverse frames or decrease the overall buckling length for increasing the critical buckling load of the ring-stiffened cylindrical shells. However, it is of no use to a large submarine . The curve r-p eo and formula are presented here, which determines whether the result of ordinary calculated methods is correct or not, estimates the maximum buckling load, determines the thickness of the shell, decides the reinforcements of structure. There is only one curve . Therefore it is convenient to use. The curve has been checked by both model experiment and exact solution. INTRODUCTION Because of the high-duty alloy being used in the large submarine, the ratio of the thickness to the radius of the ring-stiffened cylinder shell reduces and the lateral rigidity of the frames increases . For this kind of structure, the critical buckling load obtained by the ordinary method is much larger than the exact solution, the ordinary reinforcement is useless . For the structure above, in this paper, the methods are given to calculate the critical buckling load, to decide the reinforcement, to determine the maximum buckling load and to design the dimension of the structure. 1. Introduction to the problem by two practical submarines The formula for calculating the critical value of overall buckling of ring-stiffened cylindrical shell under combined axial lateral compressure is as follows  We find Eq.2 depending only on parameters A, B and r when the materials have been determined. Giving two examples of overall buckling and comparing the results of various reinforcements of the ring-stiffened cylindrical shell, we can find that there is a abnormous buckling property.