Abstract: The buckling behavior of cylindrical shells with large rectangular opening was analyzed by the finite element method. Firstly, eigen value buckling was carried out to predict the buckling mode and critical load. Secondly, the load-displacement response of the structure was computed with geometrically nonlinear analysis, and the orthogonal design method was adopted to discuss the influence of geometric parameters on the buckling load. The considered parameters include opening width, opening height, location in the longitudinal direction, and radius-to-thickness ratio and height-to-diameter ratio of the shell. The result shows that the upper limit buckling load of a cylindrical shell with rectangular opening is much less than the lower limit value of a perfect cylindrical shell, and the buckling load of a cylindrical shell with rectangular opening is mainly dependent on the radius-to-thickness ratio of the shell. The critical load declines rapidly when the radius-to-thickness ratio of the shell increases.