Abstract: The cylindrical shells and open shells with discontinuity and dissymmetry in thickness are considered as laminated shells. Based on the Hamilton canonical equation for elastic bodies, and using its semi-analytical solution, the linear equation for each layer of laminated shells is established respectively. The compatibility of displacements and stresses on the interface between layers is applied to derive the equation of the whole structure as well as the characteristic equation of natural frequencies. The major advantage of the proposed method is that it imposes no limit on the thickness of shells. The model and numerical method in this paper are also suitable for the problems of the composite laminated shells with discontinuity and dissymmetry in thickness.