Abstract: Objectives Drawing inspiration from the curved baffle structure of deep-sea ammonite shells, several bio-inspired ribbed plate designs with cross-sectional profiles of sinusoidal, sawtooth, and square-wave shapes are proposed and investigated to enhance the blast resistance of vessel plate-frame structures. Methods Using LS-DYNA simulations, the dynamic responses of plate-frame structures with biomimetic ribbed plates and conventional flat ribbed plates under underwater contact explosion loads are simulated. The blast resistance of different ribbed plate-frame structures is systematically compared, the blast resistance mechanisms and damage modes of different plate-frame structures are analyzed and revealed, and the influence laws of different rib configurations and amplitude-to-wavelength ratio variations on the blast resistance of plate-frame structures are summarized. Results The results show that, compared with the strong shear damage effect of conventional flat ribbed plates on the face plate, the novel biomimetic ribbed plates significantly suppress the shear damage of the ribbed plates to the face plate, and significantly enhance the energy absorption capacity of the ribbed plates through mechanisms such as buckling, crushing, and plastic deformation. Under the same mass condition, compared with conventional flat ribbed plates, the novel biomimetic ribbed plates can reduce the front plate breach area by up to 64.1% and the back plate breach area by 88.8%, increase the energy absorbed by the ribbed plates by 510%, and increase the critical perforation equivalent of the front plate by 84.6% and that of the back plate by 40.8%. Conclusions Compared with conventional flat ribbed plates, biomimetic curved ribbed plates can significantly enhance the blast resistance of plate-frame structures, and parameter optimization such as the amplitude-to-wavelength ratio can further improve the blast resistance of the plate-frame structures. This study provides important reference significance for the novel design and performance improvement of vessel plate-frame structures.