To comprehend the permeability behavior of modified desulfurized gypsum-based concrete under varying stress conditions, this investigation conducted permeability assessments under both confining pressure and unloading circumstances. The findings suggest that an escalation in confining pressure results in a reduction in the specimen's permeability. Conversely, a decrease in confining pressure leads to a gradual increment in permeability, albeit without fully reverting to its initial state. The rise in pore water pressure diminishes the effective confining pressure experienced by the specimen, thereby enhancing the interconnectivity of the internal pore structure and facilitating an increase in permeability. As the confining pressure intensifies, the volumetric strain also increases. Conversely, a reduction in confining pressure corresponds to a decrease in volumetric strain, though it does not return to its initial level. This observation implies that solely the elastic deformation of the specimen can recover as the confining pressure decreases. The internal pore structure distribution of modified desulfurized gypsum-based concrete is predominantly characterized by micropores, with a permeability coefficient in the order of magnitude of 10-17m2, contributing to its commendable impermeability.