Aiming at the problem of free vibration of longitudinal stiffened cylindrical shells， considering the complexity of the boundary conditions of the stringer stiffened cylindrical shell and the arbitrariness of the stringer section， the elastic constraints that can vary continuously were introduced at both ends of the shell and the displacement relationship between the displacement compatibility between the center of a stiffer with arbitrary cross section and the middle surface of a cylindrical shell was deduced， the axial mode shape function of the shell was constructed by Gram-Schmidt orthogonal method. Based on the Novozhilov shell theory， taking into account the contribution of the each translational and rotational inertia terms in the energy functional of shell and stringer， a unified dynamic analysis model for free vibration of stringer stiffened cylindrical shell was established by the Rayleigh-Ritz method.The accuracy of the results was verified by literature model. The stiffness of restrained spring was adjusted to simulate different boundary conditions， and the model is used to explore the influence of the additional position of the ribs， the number of ribs and the rib eccentricity on the natural frequency of the longitudinally ribbed cylindrical shell under the corresponding boundary. Studies have shown that within a certain range of circumferential wavenumbers： the absolute value of the difference between the natural frequency of the external ribbed and the internally ribbed cylindrical shell is positively correlated with the change of the circumferential wavenumber n； increasing the number of ribs reduces the natural frequency of the internally ribbed cylindrical shell Increasing the eccentricity of the ribs reduces the natural frequency of the internally ribbed cylindrical shell， and the effect of the eccentricity and the number of ribs on the natural frequency produces a superposition effect. The comparison between the research results and the literature verifies the accuracy and validity of the unified dynamic analysis model proposed in this paper.