<p>Heavy metal-contaminated soil will be affected by complex environmental factors such as dry-wet cycle and acid rain leaching for a long time, and the soil structure is prone to deterioration, increasing the risk of heavy metal migration. This paper used the activated MgO carbonation and solidification technology to explore the mechanical properties and Pb²⁺ migration risk of solidified contaminated soil under dry-wet cycle and acid rain leaching environment. The mechanical properties and heavy metal fixation effects of samples with different Pb²⁺ pollution concentrations were systematically evaluated. The results show that the soil strength increases slightly (1.5% -6.5%) at the initial stage of the dry-wet cycle, which is mainly attributed to the continuous hydration reaction of residual MgO during the cycle, which promotes the formation of cementation products and improves the soil structure. As the number of cycles increases, the soil structure gradually deteriorates, and the strength decreases by about 40%. In this process, the fixation rate of Pb²⁺ remains above 90%. Combined with XRD and SEM analysis, it is shown that the sample mainly generates spherulite, which gradually transforms into brucite with the increase of rounds, and the latter improves the strength more significantly. The semi-dynamic leaching test results further verify the solid soil’s low leaching characteristics (the dissolution rate of Pb²⁺ &lt; 2&#xa0;mg/L), and the sample has excellent durability and environmental safety. In summary, this study provides a theoretical basis and technical support for studying the durability of active MgO solidified/stabilized Pb²⁺ contaminated red clay.</p>