Abstract: Underground salt rock is globally recognized as the most ideal medium for oil and natural gas storage because of its good physical and mechanical properties. In China, however, the construction of underground gas storage (UGS) in salt rocks starts later, and the productivity of existing UGSs needs improving urgently. Furthermore, Chinese UGS construction is faced with the problems of deficient good salt mine resources, high construction cost and slow commissioning speed. Whereas there are a great number of old underground caverns that are formed by salt mine enterprises by means of the salt mining all around the country, the effective way to speed up UGS construction and commissioning is to rebuild UGS from existing caverns. In this paper, the existing salt caverns in Yunying area were evaluated from the aspects of sealing capacity, stability and economy by analyzing the characteristics of salt layers and the data of brine producers. It is indicated that the salt layers in Yunying area are characterized by shallower burial depth, gentle structure, good sealing capacity of cap rocks and no faulting damage. There are considerable underground caverns and they are large with thick roofs and large pillar width. Some caverns are connected between layers for they are produced by means of fracturing connection with short well spacing. By comparison, those caverns where brine is produced in the mode of horizontal well butt with larger well spacing are not damaged by fracturing and their pillar width is relatively satisfactory, so they are taken as the preferred caverns for reconstruction.