Abstract: Good cavity shape is advantageous to the release of surrounding rock stress and can effectively improve the security and stability of salt cavern gas storage. An ellipsoidal cavity is designed based on the iso-stress axial ratio theory. It is compared with the cylindrical cavity, top-enlarged cavity and bottom-enlarged cavity designed previously for shape in aspects of effective storage loss, damaged area size, floor deformation size and roof deformation of paries. As revealed by the results, the cavity based on the iso-stress axial ratio theory is more reasonable in deformation and force, and it can maintain effective capacity during the operation of the gas storage, with the least damaged area around the salt cavity and roof deformation size. Further, the shape design of salt cavern gas storage is determined by both ground stress field where the salt cavity is covered and the material of salt cave reservoir.