Abstract: A simplified jet-flow model was proposed to understand the impact effects of underwater explosion-induced gas bubbles on the structures near explosive charges. The simplified jetflow model was based on the assumption that the displacement of the bubble around a cylindrical shell structure consisted of the buoyancy-induced displacement in a free field and the pull-induced displacement by the cylindrical shell structure. And the proposed model was used to investigate the damage effect of the cylindrical shell structure subjected to jet impact and the damage mode was analyzed. The results are helpful for the study on the damage of submarines impacted by underwater explosioninduced gas bubbles.