The Daqiao gold deposit is one of the most representative super- large gold deposits in the western Qinling Mountains, China. However, the genesis of the Daqiao deposit has remained controversial. Pyrite is one of the major gold- bearing minerals of the deposit, and its mineral chemistry and in- situ sulfur isotopes can be important indicators for the genesis of the Daqiao deposit. Methods: This study presents detailed mineralogical analyses on the pyrite by using electron probe micro- analyzer (EPMA) and nanometer- scale secondary ion mass spectroscopy (Nano- SIMS).Results: Petrographic observations and backscattered electron images show that the pyrite collected from the Daqiao deposit consists of framboidal pyrite, euhedral pyrite, subhedral—anhedral pyrite, and zonal pyrite. The zonal pyrite is composed of two generations (namely core and overgrowth), corresponding to the two hydrothermal activities. Electron probe microanalysis proves that except for the framboidal pyrite, the euhedral pyrite, subhedral—anhedral pyrite, and zonal pyrite are characterized by Co/Ni ratio greater than 1 and ΔFe and ΔS less than 1, typical of hydrothermal pyrite. In particular, their (Fe+S) and As contents are well consistent with magmatic—hydrothermal pyrite from orogenic gold deposits elsewhere. Au—As correlation analysis and Nano- SIMS elemental mapping support the occurrence of Au nanoparticles within the lattice of the pyrite, which is resultant of the interactions between the pre- existing pyrite and ore- forming fluid. Nano- SIMS in- situ sulfur isotopic results show that the framboidal pyrite contains an extremely negative δ34S V- CDT value (-20.6‰ ~ -25.5‰), resulting from the bacterial sulfate reduction. Meanwhile, the δ34SV- CDTvalue of the core of the zoned pyrite ranges from +0.8‰ to +2.8‰, similar to mantle- derived magmatic sulfur. The δ34S V- CDT value of the overgrowth ranges from +8.0‰ to +17.7‰, consistent with that of magmatic rocks exposed in the western Qinling Mountains. It suggests that the latter also originated from the magmatic—hydrothermal fluids, probably with a mixture of other sulfur sources, for example, sedimentary sulfur. The difference in the S isotopes of these two- stage magmatic—hydrothermal fluids might be related to the natures of their parent magmas. Conclusion:Accordingly, the Daqiao gold deposit should be an orogenic gold deposit, which has a genetic affinity with the magmatic—hydrothermal fluids.