[Purposes] This study aims to obtain the volumetric strain and strength deterioration pattern of a compacted sand-clay mixture under freeze-thaw cycles at various remolding water contents and compaction degrees and reveal the microscopic mechanism of the change and pattern. [Methods] Studies concerning volumetric strain and unconfined compression strength (UCS) under freeze-thaw cycles were carried out on the sand-clay mixture (sand volume fraction S is 20%) at three remolding water contents (optimum water content wopt, as well as water content at dry side wd and wet side ww) and two compaction degrees (Dc is 0.80 and 0.85). Based on the microscopic observation results obtained through X-ray microscopy and scanning electron microscope techniques, the relevant mechanism was revealed. [Findings] The soil skeleton of sand-clay mixture with S being 20% is a clay-controlled type. At wopt and wd, clay aggregate takes shape with clay particles gathering together, and an aggregate-aggregate structure is formed. As Dc increases, the large pores between aggregates are compressed. At ww, the clay particles are dispersed to form a particle-particle structure. As Dc increases, the whole pores are compressed. When Dc is 0.80, samples corresponding to wopt and wd exhibit a pattern of “contraction upon freezing and expansion upon thawing”, while samples corresponding to ww exhibit a pattern of “expansion upon freezing and contraction upon thawing”. When Dc increases to 0.85, the volumetric strain pattern of samples corresponding to wopt turns to be “expansion upon freezing and contraction upon thawing”. In addition, the volumetric strain after freeze-thaw cycles of all samples is more obvious. With the increase in freeze-thaw cycles, UCS deteriorates, and the maximum deterioration rate occurs at the first freeze-thaw cycle. When Dc is 0.80, the maximum deterioration rate of UCS of the samples at different water contents in descending order is as follows: 42 kPa/cycle under ww, 29 kPa/cycle under wd, and 15.5 kPa/cycle under wopt. When Dc increases to 0.85, all the maximum deterioration rates under the three water contents are enhanced and tend to be the same value (all between 48 and 50 kPa/cycle). [Conclusions] The soil skeleton of compacted sand-clay mixture exhibits different patterns as remolding water content and compaction degree vary, influencing volumetric strain and strength deterioration patterns under freeze-thaw cycles. The findings can provide technical support for the construction, operation, and maintenance of subgrades in seasonal frozen regions.