<p>Soil salinization is a global issue that severely restricts agricultural production and engineering developments. Understanding the mass and heat transfer processes in saline soils is key to addressing these problems. In this study, a four-component coupled mathematical model, incorporating hydrological heat and solute transport with mechanical deformation within an open system was established based on permafrost mechanics with the theory of mass and heat transfer in porous media. Solute migration, heat transfer and deformation characteristics of sulfate saline soils were analyzed, and the accuracy of the model was validated by unidirectional freezing tests in a laboratory setting. During the freeze–thaw process, the linear correlation between soil temperature and ambient temperature gradually diminished with decreasing soil column height. Additionally, the heat transfer efficiency of the soil decreased exponentially as height decreased, and beyond a certain point, the soil temperature became largely unaffected by ambient temperature. The water migration and soil water potential gradient (SWPG) results indicated that the amount of water migration was dependent on the SWPG. During the prefreeze–thaw period, salt concentration increased because of the combined effects of convection, hydrodynamic dispersion and the self-purification properties of ice. This concentration then decreased as a result of the precipitation of salt crystals. The findings of this study enhance the understanding of hydrological heat and solute transport and mechanical deformation processes in sulfate saline soils, offering a valuable reference for agricultural production and engineering in saline soil regions.</p>