Abstract: The Gutaishan Au−Sb Deposit represents a typical polymetallic deposit in South China. The investigation of its mineral assemblages and ore-forming processes is essential for understanding regional metallogenic patterns. Through field geological investigations and laboratory microscopic analyses, the occurrence modes, paragenetic relationships, and chemical compositions of major metallic minerals, including native gold and stibnite, were systematically examined. The results indicate that gold mainly occurs as fracture-filling gold and inclusions within pyrite and quartz−stibnite veins, while stibnite is closely associated with quartz, reflecting typical medium- to low-temperature hydrothermal ore-forming characteristics. Mineral typomorphic characteristics reveal that the ore-forming fluids experienced multi-stage evolution, with an early high-temperature stage producing the pyrite−quartz assemblage, followed by a medium- to low-temperature stage responsible for the gold−antimony−quartz assemblage. The analysis of mineral paragenetic relationships suggests that the structural control on mineralization and fluid mixing are key controlling factors for deposit formation, and the ore-forming materials may have been sourced from deep magmatic activity and wall rock strata. This study provides a mineralogical basis for ore prospecting in this area, and contributes new case evidence to the genesis study of low-temperature hydrothermal Au−Sb deposits in South China. Future isotopic geochronological studies are recommended to better constrain the metallogenic timing and material sources.