Abstract: The Sakaerde copper deposit is a mesothermal-epithermal deposit. The δ13CPDB values of quartz and calcite samples in the deposit vary in a narrow range of -17.3‰~-0.7‰. The δ18OSMOW values range from 16.2‰ to 22.4‰, their corresponding δ18OH2O values are between 6.9‰ and 12.5‰, and the δD values of fluid inclusions vary from -73.8‰ to -52.4‰. These data imply that the ore-forming fluids of the ore deposit were mainly derived from the heated formation water mixed with a small amount of magmatic water and metamorphic water. The carbon in ore-forming fluids mainly came from formation water or atmosphere precipitation, with the addition of some deep magmatic water at the late stage. The δ34S values range from 0.2‰ to 6.1‰, implying that the sulfur in ore fluids mainly came from the magma or the upper mantle.