Abstract:The Augaro gold deposit in Eritrea is located in the Neoproterozoic metavolcanic rocks of the Nubian Shield. The ore body is mainly controlled by a NNE primary fault and near- EW secondary faults, occurring in the foliated andesite. C, O and S isotope studies of the main gold- bearing quartz vein and the altered rock ore show that the δ D w- H 2O. range of the ore- forming fluid is -68. 7‰~-49. 4‰ and the δ 18. O w- H 2O. range is -1. 9‰~4. 9‰, the range of δ 13. C v- PBD. is -15. 9‰~-10. 9‰. The S isotope composition of gold- bearing quartz vein is characterized by a small positive value with a range of 0. 18‰~0. 63‰. The S isotope composition of altered rock ore is low, characterized by a large negative value, ranging from -7. 07‰. ~-6. 86‰, indicating that the ore- forming fluid of the Augaro gold deposit mainly comes from metamorphic hydrothermal fluids, accompanied by a mixture of magmatic water and meteoric precipitation. The stratum formations and magmatic rocks in the research area provide a large amount of ore- forming materials for the gold deposit.