Abstract: The stiffened cylindrical shell structure is an important part of an underwater vehicle, and its mass directly affects the overall performance of the underwater vehicle. However, the conventional design optimization methods of the shell structure have the disadvantages of great workload and complicated calculation. This paper uses the Design Exploration module in the finite element software ANSYS Workbench to optimize the thickness of shell wall, the width and height of annular rib in cross-section, and the distance between the ribs, so as to minimize the mass of the shell in the restriction of satisfactory strength and stability. Consequently, the shell structure of an underwater vehicle is opti-mized with the proposed method, and the optimum mass of the shell structure is obtained.