This paper deals with the problem of dynamic stability of angle-ply laminated cylindrical shells subjected to impact hydrostatic pressure is described. First of all, the motion of cylindrical shells subjected to impact hydrostatic pressure is defined as an axially symmetric motion. Following this definition, certain perturbations are superimposed on this motion and their effect on the behavior of the shell is investigated. The symmetric state of the motion of the shell is called stable if the perturbations remained bounded. The solutions for the prebuckling motion and the perturbed motion are obtained using the Galerkin's method. Stable regions are determined by utilizing the Mathieu's equation. The inevitability of dynamically unstable behavior is proved analytically and the effects of various factors, such as hydrostatic pressure ratio, lamination angle and dynamic unstable mode, are clarified.