Abstract: By introducing entropy into the optimization of underground gas storage selection, a method of real weight coefficient combining inherent information of alternative projects with decision maker's subjective sense is presented. In this method, subjective weight of factors in project is determined through improved hierarchic analysis process while the external weights through information entropy, then the two are combined to gain the best weight factor to correspond with actual situations. This model is applied to 6 alternative underground gas storage design cases and it's proved to be practical and effective agreeing with both results using other methods and actual selection.