For engineering practice, conducting experiments with different stress paths to study the mechanical characteristics of rock masses is essential. In order to study the mechanical characteristics of siltstone under the special stress path of cyclic unloading-loading of confining pressure, the MTS815 rock mechanics testing system was used to conduct staged cyclic unloading-loading confining pressure tests at different axial force levels, and the evolution characteristics of axial and circumferential plastic strain and elastic modulus at different stress levels were analyzed. The relationship between the energy evolution and the deformation as well as the damage of the specimens was also analyzed via calculation of dissipated energy. The results show that the hysteresis loops move in the direction of strain increase as the number of cycles increases, and the stress-strain curves of unloading-loading confining pressure gradually close, and the overall change of hysteresis loop spacing is from “sparse” to “dense”. The lower the unloading level is, the lower the modulus of elasticity is, while the lower the stress level is, the higher the modulus of elasticity is. Modulus of elasticity is affected by both the axial force level and the unloading level; the circumferential plastic strain is generally larger than the axial value in a single cycle, and the resistance to plastic deformation at high axial force levels is stronger than that at low force levels under the special stress path; the total energy dissipated in the final damage of the rock is positively correlated with the axial force level to some extent.