Abstract: In order to explore a reasonable improvement method in sulfate saline soil to reduce the salt expansion damage of foundation projects, the lab experiment was experimentalized by using the typical saline soil in Hexi corridor of Gansu as the research object, and the salt expansion ratios of the sulfate saline soil were tested under freeze-thaw cycle conditions. The properties of sulfate salt soils were improved by adding nanometer materials (nano-calcium carbonate, nano-silica) and phase change material (PCM), and salt expansion amounts were measured on the modified sulfate saline soil. Finally, the supersaturation ratio theory and electron microscope scanning images were combined to briefly analyze the precipitation law of salt crystal and the influence of various admixtures on it. The experimental results showed that nano-silica, nano-calcium carbonate and phase change material had an inhibitory effect on the salt expansion of the sulfate saline soil. When the mix content was 2%, each of them showed good improvement effects on sulfate saline soils with no more than 3% salt content. And the improvement effects of nano-silica on salt swelling of sulfate saline soil were better than that of nano-calcium carbonate or PCM, and there existed a optial mix amount of PCM, which was about 2%.