Affected by the complex engineering environment in cold regions, it is difficult to predict the water and heat states of saline soil, and the research of the interaction process among water, heat, and salt is the core and foundation of frozen soil to reveal the mechanism of frost heave and salt heave. In this study, the crystallization temperature range of sodium sulfate saline soil was obtained through indoor test, the water-heat-salt interaction calculation model of saline soil during a cooling process was established, and the accuracy of the calculation model was verified. Results show that the crystallization temperature varied with initial salt content of soil samples; the salt crystallization for the soil samples with high initial salt content was at positive temperature, while that for the soil samples with low initial salt content was at negative temperature. The water-heat-salt interaction calculation model proposed based on the physical phenomena could effectively predict the variations of temperature, unfrozen water content, amount and distribution of sodium sulfate crystallization during a cooling process. The salt would migrate through the sodium sulfate saline soil when the crystallization occurred during a cooling process, which could increase the salt concentration and the amount of crystallization. Besides, the salt migration ability varied with initial salt content; the soil samples with high initial salt content had more salt crystallization in positive temperature range, and those with low initial salt content had strong salt migration ability in the temperature range of -4 ℃ and -6 ℃.