Abstract: In order to reveal the deformation mechanism of the ship's bottom plate subjected to the underwater explosion load, a floating body model was designed, the experimental research and theoretical analysis were carried out. Considering the spherical waves effect of the close-in explosion, the shock waves energy was obtained. The wall pressure time history measured by PVDF was used as the input load of the floating model, and the change of buoyancy on the model was considered, then the maximum kinetic energy of the model was obtained. The coupling effect of the membrane tensile strain and the bending strain is considered, the plastic deformation energy of the bottom plate was obtained by using the fitted bottom plate deflection function. The sum of kinetic energy and plastic deformation energy of the model divided by the sum of shock wave energy and bubble energy, so the energy utilization rate is obtained. The energy utilization rate increases first and then decreases with the increase of the dimensionless number Φ. When the Φ is 50～90, the floating body model has the highest utilization rate of underwater explosion energy, reaching 20%～30%.