Salt cavern reservoirs used in CAES power plants are often located deep underground, and the surrounding rock of the reservoir is in a triaxial stress state. When the cavity is formed by water-soluble mining, the original stress balance of the reservoir surrounding rock is changed, and the differential stress in the stress field will cause continuous deformation of the surrounding rock. For all rock materials, the existence of confining pressure on the one hand increases the ultimate strength of the rock and improves the bearing capacity of the rock; on the other hand, it increases the toughness of the rock, so that some of the rocks in the shallow part of the performance of ordinary hard rocks, in the deep part of the performance of the large deformation of the soft rock characteristics. With the increase of the confining pressure, the rock will be transformed from brittle response to full ductile response, which is especially important for rock salts, and the temperature and confining pressure ranges in which the transformation occurs are much smaller than those of other types of rock materials. The effect of the confining pressure on the ductility of rock salt is quite significant. Therefore, in order to be closer to the engineering reality and to reveal the creep–fatigue mechanical properties and damage evolution law of underground salt cavern surrounding rock, it is necessary to carry out triaxial rock salt creep–fatigue tests under different confining pressures on the same basis as creep–fatigue tests reported in Chap. 5 .