The Yaogangxian tungsten deposit is a typical quart-vein tungsten deposit in the Nanling region, South China. The helium and argon isotopic compositions of fluid inclusions in chalcopyrite and wolframite collected from this deposit have been analyzed. Combined with the regional tectonic evolution and geochronological data, the authors conclude that the ore-forming fluid in this deposit is a mixture of mantle fluid and crustal fluids; the former is of magmatic origin, differentiated from Yaogangxian S-type granite and enriched in helium, the latter is of meteoric origin, and the S-type granite intrusion in the mining district is ascribed to crust-mantle interaction.