This study investigated the possibility of using variation in the permeability as an index to characterize internal structural changes and fracture mechanism of a soft rock under triaxial loadings. Extensive triaxial tests were carried out on soft rock specimens to examine this idea. These tests include (1) triaxial compression tests with low and high confining pressures, (2) triaxial tests with relaxations, and (3) cyclic triaxial tests. The results of the study confirm that observation of change in the permeability provides an excellent way of characterizing the internal structural changes and fracture mechanism of the soft rock under triaxial loadings.