Baiyangping poly-metallic deposit, located in the central, slightly north of the Lanping Mesozoic-Cenozoic sedimentary basin, is one of important deposits in the famous Sanjiang metallogenic belt.C, H, O, S and Pb isotope geochemistry are discussed in this paper in order to find out sources of the ore-forming material and characteristics of ore-fluids. The δ³⁴S value of poly-metallic ore in Baiyangping deposit is between -5.6‰ and 11.2‰, with the property of thermal-chemic reduction of Mesozoic to Cenozoic evaporite sulfate in Lanping Basin. Moreover, the composition of Pb isotope in ores and sedimentary rocks of Mesozoic to Cenozoic is also very similar, which illustrates that ore-forming metal elements derive from the sedimentary rocks of the basin. The δDV-SMOW and δ¹⁸OV-SMOW of the ore-forming fluids are between -122‰ to -86‰ and -4.52‰ to -15.34‰, respectively, showing that they come from basinal hot brine, supplied by precipitation.oft-com:office:office" />