The Huize super-large Pb-Zn deposits of Yunnan Province, China are characterized by high Pb-Zn grade (Pb + Zn mostlyhigher than 25–35%) and the abundance of associated useful elements (Ag, Ge, Cd, In, and Ga, etc.). Calcite is the only vein mineral in primary ores in the orefield. This paper analyzes the carbon and oxygen isotopic compositions of 21 calcites and 4 ore-hosting strata (C 1 b). The δ 13 PDB and δ 18O SMOW of calcites are −2.1–3.5%o and 16.7–18.6 respectively and fall within a narrow range between primary carbonatite and marine carbonate (or C 1 b) in the diagram of δ 13C PDB vs. δ 18O SMOW. In combination with other geological and geochemical data, we suggest that the ore-forming fluids represent crustal-mantle fluid mixing. We believe that fluids formed from degassing of magma, accompanying magmatism of the Permian Emeishan basalts, were involved in the mineralization of the Huize super-large Pb-Zn deposits.