<p>Artificial ground freezing (AGF) technology is widely applied in undersea tunnel construction to prevent leakage and collapse by forming a frozen wall. However, the freeze–thaw process significantly alters soil pore structures, contributing to strength loss and deformation. To clarify the effects of freeze–thaw cycles and salt content on soil microstructure, X-ray computed tomography technology test was performed to investigate the silty clay under varying freeze–thaw conditions and salt contents in this study. Results revealed that freeze–thaw caused the development of elongated pores, flattened expansion of pores, complex morphology and interconnected cracks. The total porosity of the specimen increased after freeze–thaw, with a maximum growth rate of 120%. The growth rate showed an exponential downward trend with decreasing freezing temperature. A critical salt content maximizing porosity was identified-3% before freeze–thaw and 2% salt content after freeze–thaw. Low salt content favored the formation of interconnected cracks and FT intensified anisotropy. These findings provide important insights into the microstructure mechanisms of strength damage and deformation in marine soft clay under the application of AGF technology.</p>