Abstract: Site remediation plays a vital role in reducing soil contamination and mitigating associated human health risks. However, remediation activities are typically accompanied by intensive energy consumption and substantial reagent inputs, which in turn generate additional environmental burdens such as carbon emissions. Taking a chromium-contaminated site in East China as a case study, this study analyzed the carbon emission characteristics and environmental impacts of the ex-situ chemical reduction remediation project from a life cycle perspective. The results indicated that the endpoint environmental impact of remediating 1 m³ of contaminated soil was 728.12 Pt, while the carbon emissions calculated by the IPCC emission factor method amounted to 0.244 0 t CO₂-equivalent. The chemical reduction was the dominant contributor to both carbon emissions and environmental impacts, accounting for 86.63% and 69.88%, respectively. Uncertainty and sensitivity analyses demonstrated relatively low uncertainty in carbon emission estimates, with a coefficient of variation of 5.25%. The consumption of iron powder, quicklime, and ferrous sulfate were identified as sensitive parameters and key determinants of carbon emission levels. Building on the results of life cycle assessment and carbon emission accounting, targeted optimization strategies for ex-situ chemical reduction remediation were proposed, focusing on concentration-based zonation for refined remediation, low-carbon substitution for industrial by-product based chemicals, and dynamic regulation based on real-time monitoring of oxidation–reduction potential, to provide theoretical support for the development of green and low-carbon remediation practices for contaminated sites.