Abstract: Calculation theories used for lower permeability of rock salt were presented to two cases of permeability ①K<10-22 m2 and ② K>10-22 m2, that is to say, the diffusion and convective-diffusion theory and Darcy law could be used to investigate permeability behaviors of rock salt, and the formulations of the permeability for experiments in the laboratory were given. According to the experiments, the influences of the damage of rock salt on the permeability were investigated, and the results show that the permeability has hardly changed compared with permeability of natural rock salt when the stress on the rock salt is less than the stress in dilatancy criteria and there is no damage for rock salt; otherwise, the permeability will be increased rapidly. On the other hand, confining pressure makes a great impact on the permeability; and the results indicate that the permeability will decrease as the confining pressure increases under the same other conditions; in the meanwhile, experiential formulation with confining pressure taken into consideration is presented.