Abstract: To address the challenge that single remediation technology often fails to achieve standard-compliant treatment of severely heavy metal-contaminated soil from lead-zinc smelting sites, this study proposed a combined remediation process of citric acid washing coupled with iron-based material solidification/stabilization, and systematically evaluated its removal and stabilization effects on arsenic (As), cadmium (Cd), and lead (Pb) in soil. Based on the analysis of soil physicochemical properties and heavy metal speciation distribution, the treatment was carried out with 50 g/L citric acid washing followed by combined stabilization using FeCl₃ and Na₂HPO₄. The results showed that single citric acid washing achieved removal rates of 45.5%-59.9% for Cd and 56.7%-72.7% for Pb, but had limited removal effect on As. Single treatment with FeCl₃+Na₂HPO₄ could reduce the leaching toxicity, yet failed to make the leaching concentrations of heavy metals in heavily contaminated soil meet the limit requirements of Solid Waste —Extraction Procedure for Leaching Toxicity — Acetic Acid Buffer Solution Method (HJ/T 300-2007). In contrast, the combined washing and solidification process could significantly reduce both the total content and leaching concentration of heavy metals, and realize standard-compliant remediation. This study confirms the synergistic remediation effect of the combined process, and elucidates its synergistic action pathway of bioavailable heavy metals removal and residual heavy metals stabilization, which can achieve efficient remediation of soil with severe composite heavy metal contamination from lead-zinc smelting.