Abstract: In order to investigate the anti-crack effect of box girders in warship structures，model experiments are conducted to examine the crevasse size and crack extension under different stiffener conditions. Based on the experiment results，the anti-crack effect of warship box girders subjected to the contact explosion is simulated using the commercial FEM code MSC/Dytran. The comparison between the simulation data and experiments data successfully validates the proposed method. Both results show that the strength structural components（such as king-sized stiffeners）can well restrict the sizes of crevasses and the extension of cracks，and good anti-crack performance of box girders are observed in the process of anti-explosion. On the one hand，the existence of the box girder reinforces the deck stringer and upper shipboard as well as the connections between the two，which significantly absorbs the connection stresses. On the other hand，being a strength structural component itself，the box girder efficiently restrains the extension of crevasses and cracks，so that the damage degree of the whole warship structure can be greatly reduced.