Abstract: The Qingshan lead-zinc deposit is a typical altered crystalline limestone-hosted deposit in the Weining Shuicheng metallogenic subzone of lead-zinc ore cluster in northwestern Guizhou. Current research on the deposit's deep hydrothermal alteration characteristics and geochemical exploration indicators remains limited, hindering progress in deep prospecting progress. This study employs elemental geochemistry and mass-balance calculations, based on large-scale underground alteration-lithofacies mapping and systematic sampling, to quantitatively evaluate mineralization-alteration intensity using the hydrothermal alteration index (AI). The hydrothermal alteration exhibits a clear horizontal zoning outward from the ore body, it is divided into lead-zinc mineralization zone (Ⅰ), gray-gray white fine-medium crystal limestone zone (Ⅱ), gray-gray black fine crystal limestone zone (Ⅲ), and unaltered limestone zone (Ⅳ). Element migration analysis shows that ore-forming elements Pb, Zn, Cu, and Ag are strongly enriched in the mineralized zone and gradually migrated outward. The migration of Cr, V, and Mo elements is closely related to the strength of pyritization, and the migration of Ca is related to calcite and hydrothermal metasomatism. The hydrothermal alteration index effectively pinpoints lead-zinc mineralization zones, providing a reliable quantitative guide for exploring the deep and peripheral parts of the Qingshan deposit.