Nowadays, grid stiffened composite shells have many applications in aerospace. These structures include an external shell that some helical and circumferential ribs, are placed in the inner surface of shell, are being used to reinforce it. Conical shells are one of the types of these structures that are used in the construction of space projectile body. In this study, buckling behavior of grid stiffened composite conical shells under axial loading, have been investigated. For this purpose, both analytical and finite element methods have been used and effects of external shell winding, helical ribs angle, ribs number and vertex angle of cone parameters on the buckling load of these structures were investigated. In analytical method, stringers by a shell, that have equivalent stiffness, were smeared. Based on this analysis, the extensional, coupling and bending matrices associated with the stiffeners were determined. Then by use of Ritz method, buckling load was calculated. Also, in the finite element method, conical shells by use of ANSYS software was modeled and analyzed. In finite element analysis, two kinds of mode shape for these structures were observed.