Abstract: Given its good physical and mechanical properties and chemical stability, salt rock is considered to be the ideal rock mass for underground reservoir construction. To safeguard China’s energy security and strategic needs, a large number of underground salt cave reservoirs have been built in recent years. In view of the accidents caused by the instability of gas storage in foreign countries, the physical and mechanical properties of salt rock need to be investigated in depth to ensure the long-term stability of salt caverns. The damage-healing characteristics of salt rock have an important influence on the long-term airtightness of underground salt caverns. To examine the healing properties of damaged salt rock, a self-healing experiment was conducted on Brazilian cracked salt rock. Under the no-stress condition, the Brazilian cracked salt rock was healed under different humidity conditions for 120 days. The change in the permeability of the sample was quantitatively evaluated, and the damage-healing characteristics of salt rock under different humidity conditions and healing times were examined. In addition, the microscopic morphology of the damaged salt rock after healing was observed through scanning electron microscopy, and the mesoscopic mechanism of salt rock damage healing was discussed. In this experiment, the change in the permeability of the sample before and after the experiment was used to characterize salt rock damage, which effectively avoided the unreliable results obtained in previous studies through strain hardening, where the strength and elastic moduli of the samples were used to assess damage healing. The experimental results show that, under the no-stress condition, the specimens placed in the environment without external water supply are not healed after 120 days, which proves that water is a necessary condition for wound healing. Previous studies have shown that time and humidity have an important influence on salt rock damage healing. The damage-healing effect on salt rock increases with time and humidity. However, the rate of increase decreases exponentially, which indicates that excessive humidity and time do not effectively improve the damage-healing effect on salt rock.