Abstract: The Dongtongyu gold deposit is located in the middle-west part of Xiaoqinling gold ore field. The ore bodies are controlled by the ductile shear zone. In this paper, the authors systematically studied C, H, O and S isotopic compositions of the three mineralization stages in order to define the source of ore-forming fluids and metals.The δD values of 12 quartz samples from different stages range from -78.1‰ to -42.2‰. The δ¹⁸OH₂O values of 12 quartz samples fromthree different stages vary from 9.76‰ to 13.16‰, from 6.30‰to 8.10‰ and from 6.76‰ to 7.26‰, respectively. The δ¹³C values of CO₂ in fluid inclusions change from -1.8‰ to 2.5‰.The δ³⁴S values of 16 sulfides samples in this deposit vary from -3.7‰ to +8.2‰. The hydrogen and oxygen isotopic compositions indicate that these ore-forming fluids were mainly sourced from the magmatic water and metamorphic water. The carbon in ore-forming fluid was mainly sourced from mantle materials. Based on the sulfur features, the authors hold that the metals of the Dongtongyu Gold Deposit were derived from Taihua Group or magmatic rocks.