Abstract: The existence of thick interlayer makes the salt-cavern leaching more difficult during the construction of salt -cavern gas storage, and impact the cavern shape in different degrees. In order to make full use of salt beds, therefore, it is necessary to study the collapse process of thick interlayer and its control technologies. In this paper, an interlayer of 12 m thick in one salt-cavern gas storage in China was taken as the example for study, and two wells were selected for field tests. It is indicated that the probability of integral instability and collapse is lower if the thick interlayer is taken as the direct roof of cavern. If the diameter of the thick interlayer is large enough, partial damage tends to occur along the wellbore when solution mining is carried out simultaneously above and below the interlayer, and consequently the interlayer will be collapsed in the large area. It is shown from the analysis on the field data that the thick interlayer with diameter of 60 m by controlling the downhole technologies can not only lead to the collapse of thick interlayer in the large area, but also reduce the complexity of the downhole process. The research results can be used as the reference for processing the thick interlayer of salt-cavern gas storage.