Abstract: The deformation mechanism of a ship bottom floor when the ship runs aground over sharp rocks is analyzed, based on plastic mechanics theory and numerical simulation technique. Numerical simulation using the code LS_DYNA is first conducted for understanding the behavior of bottom floors and establishing the analytical models. Then the analytical expressions of the resistance of a bottom floor are derived and the accuracy is verified by numerical simulations. The proposed analytical method can be used to predict the ship bottom structure crashworthiness during the structural design phase.