Abstract: To get a lightweight anti-blast structure, short-cut glass fiber reinforced composite (SMC) and carbon fiber reinforced plastics (CFRP) were adopted to design and make stiffened plate. Finite element simulation based on LS-DYNA reveals that the composite stiffened panel has excellent anti-blast ability through large elastic deformation and the panel will rebound back completely with little residual deformation. Parametrized analyses reveal that transverse bars greatly influence the maximum flexure of the stiffened plates under blast. Their contribution to the rigidity of the panel is much greater than the longitudinal reinforcement and the skin. Applying equivalent volume conversion method, the stiffened panel is simplified as a uniform panel and the dynamic response of the composite stiffened panel is predicted theoretically. Precision and validity of the prediction in flexure are testified by the numerical simulation.