Abstract: The Nibao gold deposit, Pu`an county, southwestern Guizhou, which includes both stratabound and fault- controlled gold orebodies, constitutes an important part of the Yunnan—Guizhou—Guangxi “Golden Triangle” region, and is one of the major breakthroughs in gold prospecting in recent years. The isotopic composition of gold- bearing quartz from the Nibao gold deposit, defines Rb- Sr isochron ages of 141±2 Ma and 142±3 Ma for stratabound and fault- controlled orebodies respectively, which corresponds to the time of gold and antimony mineralization as well as regional magmatic activity. This relationship implies that the Nibao gold deposit possibly formed in an extensional environment related to subduction of the circum- Pacific plate. Fluid inclusions and stable isotopes (H, O, S) show ore- forming fluids mainly originate from deep magmatic sources, which contains a certain amount of metamorphic water and precipitation. Fluids are medium—low temperature, have low salinity and are hyper- pressurized. The mineralization environment is weakly acidic to reducing. We propose a deep- sourced magmatic model for formation of the Nibao gold deposit. Deeply- sourced mineral- bearing hydrothermal fluids upwell along deep factures and are transported to shallow depths, due to the change of the physical and chemical conditions, Fe- poor and Au- rich fluids react with active iron in the ore- hosting rock through sulfurization which migrated with Au(HS)2-, Au(HS)0in ore- forming hydrothermal, and form gold- rich and arsenic- bearing pyrite, resulting in the deposition and enrichment of a huge amount of Au. Gold deposits formed by depositing the enriched Au in favorable ore- hosting spaces (fault F1, Sbt, anticline cores and interlayer fracture zones) and ore- hosting rocks (sedimentary tuff and tuff).