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The Beiya porphyry-sk gold-polymetallic deposit is one of the largest gold deposits in China and it also contains significant amounts of silver and base metals.The ore-bearing monzonitic granite porphyry occurs as a stock,of which the sk type gold-copper-iron ore bodies are controlled by the contact zone between alka-li-rich monzonitic granite porphyry and the limestone,and the gold-silver polymetallic mineralization is con-trolled by interlayer structure.Alteration and mineralization occur around the intrusion and exterior of monzonit-ic granite porphyry.Ore mineral formation sequence is as follows:sk minerals→magnetite→pyrite→chal-copyrite/bite+pyrite+gold→pyrite+galena+gold (silver).Petrographic studies of fluid inclusions indi-cate that the following types of inclusions exist in the pre-mineralization quartz-pyrite stage:gas-liquid two-phase inclusions (L-type ),three-phase inclusions with daughter minerals (D-type )and gas-rich inclusions (V-type).The colorless transparent quartz in the main gold-chalcopyrite-pyrite stage mainly consists of L-type and V-type inclusions,whereas the inclusions in the late gold-silver-galena stage are mainly L-type.The evolu-tion of ore-forming fluids shows a trend from high temperature,high salinity to medium-low temperature and low salinity.Medium-low density fluids play a dominant role in mineral component migration and transportation. Fluid cooling and boiling are the main mechanisms of gold-copper precipitation,while the involvement of atmos-pheric water and pH reduction are the main mechanisms of gold-silver polymetallic precipitation.The fluids in the quartz-pyrite stage before mineralization and the main gold-chalcopyrite-pyrite stage are dominated by mag-matic water,while in the gold-silver-galena stage the fluids are dominated by atmospheric water.Isotope tracers show that S and Pb are mainly derived from monzonitic granite porphyry,not from limestone of the Beiya Forma-tion.