Abstract: [Objectives]Underwater explosions can cause severe damage to ship structures and pose a threat to the survivability of naval vessels. Currently, the side protection structures of large ships often adopt the traditional "air cabin-liquid cabin-air cabin" triple-cabin structure, which is cumbersome and relatively inefficient in terms of protection. Therefore, it is essential to seek improvement and innovation to enhance the underwater protective performance of ships. [Methods] In this study, a numerical model based on the Arbitrary Lagrangian-Eulerian (ALE) algorithm was established. The accuracy of the ALE algorithm was verified through typical structural contact explosion cases. Based on this, models of both the traditional triple-cabin protective structure and the cylindrical protective structure were established. By comparing and analyzing the characteristic parameters such as maximum stress and strain after underwater contact explosion with the same charge, the degree of structural damage and energy absorption differences were evaluated to assess their respective protective performance.[Results]The study found that the displacement of the longitudinal wall defended by the cylindrical protective structure was smaller than that of the watertight longitudinal wall, which is contrary to the behavior of the traditional triple-cabin protective structure. Additionally, the energy absorbed by the deck and bottom plate of the cylindrical structure is 9.92% less than that of the traditional protective structure, demonstrating a significant advantage in resisting deformation in the vertical direction.[Conclusion] The cylindrical protective structure exhibits lower levels of damage under the same charge, providing new insights for the innovative design of underwater protection structures.