<p>Microbially induced carbonate precipitation (MICP), a new soil solidification technology, can effectively repair Pb²⁺ contaminated soil. However, heavy metal ions have toxic effects on microorganisms, inhibit urease activity, and reduce solidification efficiency. The natural environment of dry–wet alternation will also destroy soil structure. To further enhance the remediation effect of MICP solidified Pb²⁺ contaminated soil, this paper proposes introducing MgO to cooperate with MICP, thereby strengthening the remediation efficiency of Pb²⁺ contaminated soil. The unconfined compressive strength test, direct shear test, fracture quantitative analysis, toxicity leaching test, and XRD test were investigated under a dry–wet cycle. The effects of the MICP-MgO composite system on the strength evolution of Pb²⁺-contaminated soil, the inhibition mechanism of fracture development, and the stabilization effect of Pb²⁺ were revealed. It fills the gap in current research on the remediation of heavy metal-contaminated soil using MICP combined with MgO under a dry–wet cycle. The results show that when the MgO content is 5%, the strength of Pb²⁺ contaminated soil can be significantly improved, and the compressive strength, shear strength, cohesion, and internal friction angle of the sample are significantly enhanced at the initial stage of the dry–wet cycle. At the same time, the dosage can effectively inhibit the crack propagation induced by the dry–wet cycle, making the Pb²⁺ leaching concentration of the soil stable below the standard limit after the repair. It provides new insights for the long-term, stable remediation of sites contaminated with heavy metals.</p>