Abstract: Plate frame is the main structure of ships. With the AUTODYN common software，numerical model of the plate frame by underwater contact explosion was established by the couple of the Largange and Euler code，and the simulation results agreed well with the experiment failure mode. Then，the whole failure process of the plate frame by underwater contact explosion was analyzed，and the formation and extension of the crevasse with failure mode of reinforcement was discussed. Besides，the failure mode coupling effect of the plate frame and reinforcing plate was proposed. The results demonstrate the damage characteristics of the plate frame.