For underground gas storage reservoir the stress state may be changed by cyclic injection and depletion of natural gas. The change of stress state may have a significant influence on the poro-mechanical properties of reservoir rocks. In this research the poro-mechanical properties evolution under hydrostatic stress after induced damage is investigated. At constant confining pressure deviatoric stress is maintained at a constant value (smaller than the peak stress value) and then unloaded to zero. Because of damage the material is thought to be transversely isotropic. Biot's coefficient in axial direction and lateral direction is measured when deviatoric stress is unloaded to zero. This procedure is repeated several times with cyclic loading-unloading of deviatoric stress (the value of deviatoric stress increased gradually). Generally, it is found that the Biot's coefficient in axial direction gradually decreased with the increase of cyclic numbers while the value in lateral direction gradually increased. The reason is that the induced micro-cracks are mainly oriented in the axial direction such as more irreversible micro-cracks will still exist with the increase in deviatoric stress since in lateral more and more micro-cracks will be compressed.