Abstract: When ships are sailing in rough seas, the structures of ships are subjected to severe slamming induced by waves. These impact loads will make hull structures buckle, and then inactivate the whole load carrying capacity of marine structures and brings in a catastrophic end. It is vitally important to study on the dynamic behavior of stiffened plates, which is one of the fundamental structural components of ship structures. On the basis of discrete stiffened plates model, the dynamic response of imperfect rectangular stiffened plates with elastically restrained edges under in-plane fluidsolid impact loading is investigated theoretically in this paper. The spline function is chosen to describe the deflection. The governing equations of the dynamic response Of imperfect stiffened plates are obtained by weighted residual method. The equations are solved by a four th-order Runge-Kutta method, and the homologous computer code is developed in FORTRAN. The formed B-spline function is adaptable to any elastic restraints against rotation. The influence of initial geometric imperfecti on, load duration, stiffeners and elastic restraints are discussed. The results indicate that they are important factors affecting stiffened plates＇ dynamic behavior. The load carrying capacity of stiffened plates will be enhanced if the elastic restraints are increased properly or the initial geometric imperfection and load duration are decreased.