In this paper, simulation and analysis of thin steel cylindrical shells with elliptical cutouts under oblique loading were studied using finite element method. First, the numerical results were validated by the results of experimental test performed by an INSTRON 8802 servo hydraulic machine. Also, the effect of cutout angle (θ), cutout size, cutout position (L0/L) and cutout aspect ratios (b/a) were investigated, where parameter (a) shows size of the cutout along longitudinal axis of the cylinder, parameter (b) is size of the cutout in circumferential direction of the cylinder on the buckling and post-buckling behavior of cylindrical shells with finite element method. It can be concluded that increasing width of the cutout extremely decreased the buckling load while the cutout height was constant. Moreover, changing position of the cutout from the mid-height of the shell toward the edges increased the buckling load.