Abstract: Cylindrical shell is the key part in ships and offshore structures, and accurate prediction of the dynamic response and shock damage of the cylinder model makes good sense. In this paper, a cylindrical shell consisting of twin cavities was designed to simulate the structure with stuffing, which is called hard model compared with the soft model without sand inside. The dynamic responses and shock damages of the test models subjected to underwater shock wave loadings detonated by spherical TNT explosives were investigated. Different tests were conducted by changing the TNT charge weight, standoff distance, explosion position and model type. Furthermore, the experimental results are compared. Detailed discussions on experimental results show that the dynamic responses and damage modes are much different; the hard cylindrical shell has better resistance than the soft one when exposed to underwater explosion. The shock damage is mainly observed at the instrument capsule of the hard model while the main capsule of the soft one manifests axial tearing of the shell.