Abstract: Using a self-developed one-dimensional visual horizontal freezing device, one-way horizontal freezing tests were conducted on soft clay under various temperature gradients. The development of the cryostructure in the longitudinal section of the soil was observed. The results indicate that water migration during the horizontal freezing process induces thermal responses, including variations in temperature, water content, pore-water pressure, and soil pressure, with the temperature gradient being the primary driver of water migration. During the horizontal freezing process, bidirectional water redistribution occurs in the soil due to gravitational effects; however, horizontal water migration is significantly greater than vertical migration. After 120h of freezing, the water content within the freezing zone is markedly higher than the initial water content, with the maximum often observed at 1~3 cm from the freezing front. Conversely, the water content in the unfrozen area is generally lower than the initial value, indicating dehydration consolidation in this region. Additionally, the longitudinal section of the soft clay exhibits a distinct and pronounced cryostructure during the horizontal freezing process, primarily resulting from increased tensile stress due to low-temperature suction and crystallization stress. Based on the shape, density, and distribution characteristics of the cryostructure, it can be qualitatively categorized into whole shapes, fiber layers, thin layers, and thick layers. The findings of this study provide preliminary insights into the water-heat-force-structure response processes of soft clay during horizontal freezing, offering a necessary theoretical foundation for elucidating the mechanisms of horizontal frost heave.