The Huaniushan gold deposit is located in the south of Beishan orogenic belt.The orebody is hosted in the contact zone between the Indosinian K-feldspar granite veins and marble.The mineralization process can be divided into early skarn stage and late quartz sulfide stage（main metallogenic stage）.The fluid inclusion properties of quartz and calcite in the main metallogenic period indicate that the ore-forming fluid has the characteristics of medium-low temperature，medium salt，medium-high density，and with CO₂ and CH₄，which belongs to the H₂O-CO₂-NaCl system.The temperature-salinity characteristics indicate that the ore-forming fluid is the mixture of magmatic water and atmospheric precipitation.The average value of δ¹³C_V-PDB，δ¹⁸O_V-PDB and δ¹⁸O_V-SMOW of calcite is 1.7‰，-22.5‰ and 7.69‰，respectively，and the O isotope strong differentiation suggest that magmatic water mixed with atmospheric precipitation to form ore-forming fluids.The average value of sulfur isotope δ³⁴S of pyrite in the ore is -9.73‰，and its large negative value may be related to the surrounding rock strata，indicating that the sulfur source of the deposit may be a mixed source of magma and strata.The metallogenic depth and pressure features hint that the Huaniushan gold deposit belongs to the shallow metal-logenic depth.Comprehensive analysis shows that Huaniushan gold deposit is a medium-low temperature hydrothermal metasomatic （skarn type） gold deposit.Summarily，in the late Triassic，Huaniushan area expe-rienced multi-stage post-orogenic lithospheric extension and mantle-derived magma underplating，the ore-forming fluid produced in the deep and moved upward along the fracture，reacted with the surrounding rock and mixed with atmospheric precipitation.With the pressure decreasing，the ore-forming materials were precipitated and enriched，and initiated the gold mineralization.