Abstract: With the Hamilton canonical equation of cylindrical shells, the coupling equation of an elastically constrained circular cylindrical double-shell system is derived. It is employed to analyze the vibration behavior of a large generator stator system. A semi-analytical method with no assumption of stress and displacement is developed, in which the thickness of shell is not restricted and the uniform distribution of springs is not needed. Like the general finite element method(FEM), the present approach can deal with complex boundary conditions and structures made of multiple materials. With less unknown quantities than that of general FEM and convenient data preparation, the present approach exhibits fast calculation speed. Therefore, it suits for engineering practices.