The layered salt rock formation in China has the characteristics such as thin in depth, too many interlayers, and high impurity contents. The vertical gas storages sometimes couldn’t get enough volume to meet the demands of economy when the thickness of the salt layer is thin. By improving the horizontal dimension, the horizontal gas storages were built in the salt formation which didn’t have interlayers could satisfy the demands of economic volume. To discuss the mechanical feasibility of horizontal gas storage, we propose the simplified mechanical model of horizontal ellipsoidal gas storage. Using the elastic theory method, we acquire the computational formulas of stress distribution of the key points with the help of other researchers’ results, which are the function of ellipsoid shape ratio, the material Poisson’s ratio, the operating internal pressure and the far field stress. The theoretical solution and numerical solution are compared; and the average error is about 3%. Taking Druker-Prager yield criterion into account and by applying the theoretical formula, we calculate the minimum operating internal pressure when the horizontal ellipsoid shape ratio kept constant, acquire the relationship between ellipsoid shape and the minimum internal operating pressure and discuss the range of operating internal pressure of the horizontal ellipsoid gas storage.