Abstract: The design conditions about a ship similar model under the action of bending and torsion were derived based on the thinwalled beam theory, and then one method about independently dealing with stiffeners and plates was presented. One container ship was studied as an example, a mathematic model optimizing the similar model was set up, and then based on multiisland genetic algorithm the unfeasible design was improved into the feasible region. Using the nonlinear FEM method validates the consistency of the real ship’s and similar model’s ultimate strength under the action of bending and torsion, so the similar model can be used to test the real ship’s ultimate strength.