Abstract: The Gaotongling molybdenum deposit is located in the Wuzhishan fold belt of the South China fold system, Southern China plate. Nine orebodies of economic value and five mineralized bodies which are approximately parallel to each other have been identified. Ores are mainly of sulfide quartz vein type and K-feldspar granite type. The ores are composed mainly of sulfides such as molybdenite, pyrite, chalcopyrite, galena and sphalerite and gangue minerals such as quartz, potassium feldspar, biotite, sericite and chlorite. The molybdenum content in the Gaotongling granite intrusion is 4 times higher than its clarke value. Potassic alteration, pyritization, silicification, sericitization and chloritization, as well as molybdenum mineralization are observed along structural fractures in the granite intrusion. The ore-forming fluids are of K+-Na+-Cl--F--SO42- type. The sulfur, carbon, hydrogen and oxygen isotopic compositions suggest that the ore-forming materials were mainly derived from magma and that the ore-forming fluids originated by mixed sources of magmatic water and meteoric water. The Re-Os isochron age of molybdenite is 98.4±2.5 Ma, which coincides with the emplacement age of the Gaotongling granite intrusion. It is concluded that the deposit is a hydrothermal sulfide-quartz vein type deposit genetically related to Late Mesozoic (late Yanshanian) granitic magmatism.