Abstract: In this paper, the authors carried out the study of the carbon-oxygen-strontium isotope geochemistry of the samples from deep holes during the mineral prospecting work in the Qixiashan Pb-Zn polymetallic deposit. The results show that the δ¹³C_V-PDB values for ore samples from the Qixiashan deposit vary from -5.1‰ to 1.9‰. From the shallow part downward, the δ¹³C and δ¹⁸O values of ore samples are in an increasing trend, which indicates that the carbon in the ore-forming fluids originated from the carbonate rocks and from the deep source of carbon in the mantle and magma. In the study of strontium isotope, the ⁸⁷Sr/⁸⁶Sr values of ore samples from the Qixiashan deposit vary from 0.704816 to 0.71405; a part is larger than the ⁸⁷Sr/⁸⁶Sr ratios (0.708329~0.709685) for limestone of the Huanglong strata, which is the surrounding rock of the orebodies, whereas the other part is less than ⁸⁷Sr/⁸⁶Sr ratios for limestone of the Huanglong strata. A comparison of the strontium isotopic compositions of different sources reveals that the strontium from the Qixiashan deposit has the characteristics of the mixed sources, i.e., the strontium of Proterozoic basement strata and the mantle source; the change of ⁸⁷Sr/⁸⁶Sr ratios in the surrounding rock alteration should be mainly caused by the ore-forming fluid, and the change of ⁸⁷Sr/⁸⁶Sr ratios in the process of wall rock alteration should be mainly caused by the ore-forming fluid. A comprehensive analysis of regional metallogenic geological characteristics shows that the ore-forming fluid in the Qixiashan deposit might have come from the granite hydrothermal period, and by the influence of thermal power, the ore-forming fluid flowed through the Proterozoic basement strata, forming the ore-forming fluid with mixed material sources. The mineralization process of the Qixiashan deposit was mainly caused by the fluid-rock reaction between the ore-forming fluid and the surrounding rock.