The Dachang Tongkeng deposit in Guangxi is a world-class supergiant deposit, with long-standing research extensively elucidating its tin-polymetallic mineralization processes and enrichment mechanisms. In recent years, Ag-Zn polymetallic ore bodies have been discovered during mining development, yet studies on the genetic mechanism of this mineralization type remain extremely limited. This knowledge gap significantly constrains the comprehensive understanding of metallogenic processes in the Tongkeng deposit and hinders further exploration of polymetallic mineral resources. Focusing on the Ag-Zn mineralization, this study investigates the evolution of ore-forming fluids and material sources through fluid inclusion microthermometry, C-H-O-S-Pb isotope analyses, and field geological investigations, while exploring the genetic mechanism of Ag-Zn polymetallic mineralization and its intrinsic connections with other ore bodies.The homogenization temperatures of ore-forming fluids range from 102 to 321°C, with salinities of 1.2%–14.63% NaCleqv. Quartz H-O isotopes (δD=-59.8‰ to -57.9‰; δ₁₈^O_H2O=4.85‰~11.06‰) and calcite C-O isotopes (δ₁₃^C_V-PDB=-9.14‰~1.47‰; δ1?O_H2O=3.01‰~6.80‰) indicate that magmatic hydrothermal fluids constitute the primary source of ore-forming fluids, with late-stage mixing of meteoric water accompanied by water-rock interactions, driving fluid evolution from medium-high temperature/salinity to medium-low temperature/salinity. Sulfur isotopes demonstrate dominant magmatic sulfur sources with localized sedimentary sulfur contamination, while lead isotopes reveal predominantly upper crust-derived metals with minor mantle contributions. Sulfur-rich hydrothermal fluids generated by magmatic differentiation migrated along fault systems. During decompression and cooling, mixing with meteoric water altered physicochemical conditions through water-rock interactions, triggering precipitation of Ag-Zn sulfides. The deposit represents a product of interactions between magmatic hydrothermal systems and wall rocks, characterized by magma-dominated metallogenesis coupled with multi-source fluid co-evolution.