Abstract: Analyses on the long-term deformation of gas storage caverns in a salt dome were carried out using the 3D-FEM. The stresses in salt rock surrounding a cavern are lower than those in the virgin ground and with distribution as hydrostatical pressure surrounding a pumping well.The surplus storage capability of one of the caverns will remain 29.1% of the original value after 80 designed operation years. Further researches show that the above mentioned value will be greater when the cavern space is larger. The surplus storage capability of one of the caverns with a space of 400 m is 5 to 10 percentages greater than that with a space of 280 m.