Abstract: The numerical creep analyses on salt rock surrounding a gas storage cavern using the FDMsoftware FLAC3D show that, since salt rock creeps heavily under stress, the stable stress field in the salt rock strata has the characters of hydrostatical pressure, which is very important for the stability of salt rock surrounding a cavity. Under an average inner gas pressure of 6 MPa, which is designed for a salt cavern located at 1000 m to 1340 m depth, the surplus storage capability of the cavern will remain 275% of the original capability after 80 designed operation years. Taking into account the scale and boundary condition effects of the model, the numerical results have been proved to be a relatively conservative reliable valuation.