Abstract: The dynamic response process and the instability of convex ring-stiffened cone-cylinder combined shell with the deep-water explosion load in the range of 300~500 m depth was obtained by ABAQUS numerical simulation method. Based on the stability criterion of the structural deflection change, the critical instability load and deflection of the cone-cylinder combined shell under different parameter conditions was summarized and the factors affecting the stability of ring-stiffened cone-cylinder combined shell were evaluated. The results show that there are three different instability mode with different structure dimension parameters, and the water depth conditions, the shell radius, the shell thickness, and the cone angle of the ring-stiffened cone-cylinder combined shell have a great influence on structural stability, while the thickness of the ribs has little effect on the structure stability. Finally, a calculation formula for structural critical instability in common instability mode is established by dimensional analysis.