Abstract: The Sonar trunk is the working environment of sonar. When warship is subjected to noncontact underwater explosion, the sonar trunk will probably yield so large deformation that sonar can＇t work properly. In this paper, the three-dimensional finite element model of a warship is created with numerical software, and on the basis of this, when the warship is subjected to underwater explosion in a specific working condition, the deformation of the corner points and the walls of the sonar trunk are studied with the coupled acoustic-structural arithmetic. The validity of the model is verified with two methods--comparing both the total mode and the local mode. Furthermore, various means of optimization are adopted for the region where the deformation is extremely large. Taking the effects of different factors into account, through numerical calculation and comparis on, the best optimization scheme is obtained to offer a reference in the design of the sonar trunks of warships.