Abstract: In order to explore an optimization design method to design explosion protection stiffened plates, finite element modeling was carried out to simulate the response of clamped rectangle single stiffened plates subjected to blast load. Failure modes of the stiffened plates were analyzed. The influence of relative rigidity and intensity of the blast load was studied. The 3 types deformation modes of failure mode Ⅰ and 2 types of sub-failure mode of failure mode Ⅱ were put forward. The approximate formula to predict the largest deflection of stiffener and the stiffened plates and the criteria of the 2 failure modes were proposed. At last, the optimization design of single stiffened plates subjected to blast load was performed. The results show that it is feasible to optimize the structure of explosion protection stiffened plates, when the critical conditions of transformation from large plastic deformation (failure mode Ⅰ) to breakage damage (failure mode Ⅱ) are acquired by numerical simulation or experiment. The relationship between the mass of stiffened plates and the dimension and space of the stiffeners can be derived from these critical conditions, under the condition that the explosion protection capability of the stiffened plate is best. Thereby the optimization design of explosion protection stiffened plates can be achieved.