Abstract: The warships have to take measures against attack grom anti-ship weapons. When either before and after the main deck of ship hull is directly attacked by the laser-guiding bomb GBU-12B/ B, the change of strength is comparatively analyzed, and the concept that the box-girders added under main deck is given to improve the resistance capability of structure damage. The stress on the crevasse of deck struck by the bomb is computed by the finite element model, and analyzing the structure with box-girdersas how it impact the residual strength of ship. The results of analysis shows that the hull structure with the box-girders added under main deck improves the residual strength of ship, resulting to improve ship survivability.