Winter freezing and spring thawing cause engineering geological issues such as frost heave cracking, thaw settlement, and boiling subsidence in sulfate saline soil embankment construction. To this end, freeze-thaw test, unconfined compressive strength test, SEM test and CT test were completed on sulfuric saline soil stabilized with lime, SH agent, and fiber to study the mechanical properties degradation and the microstructure damage characteristics under freeze-thaw conditions, clarifying the influence mechanism of the SH agent and fiber on the freeze-thaw durability of the soil. The results show that the UCS of soil exhibited a stage-wise change, with a large decrease, small decrease and stable strength as the number of freeze-thaw cycles increased. With the increase of freeze-thaw cycles, the area ratio and the equivalent diameter of soil particles decreased, some aggregates were broken, and the morphology of soil particles gradually transitioned from elongated to circular. Fiber reinforcement reduces the porosity of soil, and the number of small pores gradually reduced, and the number of medium pores and large pores increased little by little. The number of cracks increases, and they gradually extend from the surface of the specimen into the interior. Sulfate saline soil stabilized with 12% lime, 3% SH agent and 0.3% fiber is a more suitable mix ratio. SH agent wraps soil particles and fills soil pores, as well as the interface interaction between fibers and soil and the spatial network structure formed by fibers, which improves the mechanical properties and freeze-thaw resistance of sulfate saline soil.