Abstract: Sulfate saline frozen soils are widely distributed in western China, where engineering issues related to salt heave, frost heave, settlement, differential settlement, and foundation corrosion have become increasingly significant. This study focuses on sulfate saline frozen soils prevalent in western China and treats them with different types and dosages of soil modifiers. The variations in shear strength before and after improvement were investigated through static triaxial tests conducted at subzero temperatures under different thermal conditions. The test results show that the maximum principal stress difference of sulfate saline frozen soil decreases as temperature rises. Compared to the value at 2 ℃, the maximum principal stress difference at-5 ℃ and-9 ℃ increased by 2.91% and 10.68%, respectively. Among the modifiers tested, cement had the most pronounced effect on improving the maximum principal stress difference, followed by quicklime and fly ash. While fly ash at dosages of 4% and 8% did not significantly affect the maximum principal stress difference, using 8% cement, 8% quicklime, or 12% fly ash led to a more rapid increase. Specifically, compared to untreated soil, these treatments increased the maximum principal stress difference by 43.48%, 30.43%, and 39.13%, respectively. Furthermore, all modifiers improved both cohesion and internal friction angle to varying degrees. Quicklime and fly ash increased cohesion by approximately 25%, whereas cement at a 12% dosage raised cohesion by about 77.88% and increased the internal friction angle by about 11.68%. These findings provide a reference for foundation treatment in sulfate saline frozen soil regions of western China.