During the operation of a salt cavern CAES power plant, the level of gas injection pressure determines the energy storage capacity of the CAES, and the change of gas injection pressure also affects the damage evolution of the surrounding rocks of the reservoir. Acoustic Emission (AE) technique is an effective tool to study the damage evolution patterns of materials such as metals and rocks. When a material is subjected to external loading, the sudden redistribution of stresses (due to microcracking/deformation) converts mechanical energy into acoustic energy, resulting in the generation of elastic waves. This phenomenon is known as acoustic emission and is a concomitant to stress redistribution in internal structures. Rock research on AE first began in 1941, by Obert rock explosion monitoring in mines. However, the AE signal strength of many materials is very weak (a human ear cannot directly hear it), so there is a need to use sensitive electronic instruments to detect, record, analyze AE signals. In 1950, the German scientist Kaiser took the lead in studying the AE characteristics of engineering materials. With the continuous development of electronic technology, the reliability of AE technology is also improving. Scholars around the world have conducted many studies on the mechanical properties of rocks based on AE monitoring of fatigue, compression, tension and creep. Evaluating the structural stability of rock materials by AE signal parameters (counts, energy, peak frequency, duration, etc.) is a widely used method, which is fast and intuitive. And on the fact that by a refine analysis of AE signals, it is possible to determine the location of microcracks, but distinguish different types of damage (size of cracks). In this Chapter, we will focus on the damage evolution of rock salt under the influence of different confining pressures and stress levels with the help of AE techniques.