Abstarct: During the last decade, the storage of gas produced from hydrocarbon fields in the hot seasons of the year and its recovery in the cold seasons, which increases the need for domestic and industrial use, has been a major concern among the countries that produce and consume this type of fuel. Natural gas storage in salt cavern has been one of the solutions to this problem. One of the important challenges in this method is the integrity of the cavern well during its long-term life due to the presence of various influencing factors in two categories of geomechanical and operational factors. The purpose of this research is to investigate the role of the mechanical properties of the contact surface of salt and cement. Accordingly, first, laboratory studies on the sample of salt cores and three combined salt-cement cores were made and tested to obtain the mechanical properties of its contact surface. Then, using numerical modeling in FLAC3D software, a salt cavern model was built using the information of one of the studies in the history of the subject and its results were validated. The results of this section showed that the constructed model had a high agreement with the reference model. In the sensitivity analysis stage, the mechanical parameters of rock salt, cement, salt-cement contact surface, stress conditions around the well and internal loading of the well due to gas pressure were examined in a constant and cyclical manner. The results showed that in the conditions of constant internal pressure of the well and hydrostatic conditions of stress around the well, the role of parameters of elastic modulus and Poisson's ratio of cement and rock salt in the well integrity is very prominent and the effect of the mechanical properties of the salt-cement contact surface on well integrity evaluation criteria is not noticeable. However, in the conditions of cyclic loading, the amount and range of shear slips of the salt-cement contact surface increased significantly, and its value decreased with the increase of the normal and shear hardness of the contact surface. Also, by increasing the difference between the maximum and minimum pressure, the amount of slip on the contact surface increases, and in this case, increasing the normal and shear hardness of the salt-cement contact surface has been effective. In addition to the mechanical properties of rock salt and cement, gas pressure and exploitation cycles, it is very important to pay attention to the mechanical properties of the salt-cement contact surface in the design and exploitation phase of the cave due to the creation of areas with the potential for gas leakage.