Abstract: The Saibagou gold deposit, located in the Wulan area, eastern part of the northern Qaidam metallogenic belt, is one of the representative gold deposits in the northern Qaidam metallogenic belt. Recently, new breakthroughs have been made in prospecting at the deep and peripheral areas, but the genetic mechanism of the deposit is still controversial. Fluid inclusions and H-O-S-Pb isotopes of gold-bearing quartz veins from the Saibagou deposit are examined in this study. The results show that the fluid inclusions in the Saibagou gold deposit are mainly characterized by gas-liquid two-phase inclusions and CO₂-bearing three-phase inclusions. The homogenization temperature of the inclusions ranges from 200 ℃ to 320 ℃, the salinity ranges from 0.18% NaCl_eqv to 14.67% NaCl_eqv, and the fluid density ranges from 0.67 g/cm³ to 1.13g/cm³. These lines of evidence support an ore-forming fluid characterized by medium temperature, medium-low salinity and low density, and belonging to the H₂O-NaCl-CO₂ system. The δD_V-SMOW values are between −75.1‰ and −65.2‰, and δ¹⁸O_H2O values are between 2.3‰ and 3.3‰, suggesting that the ore-forming fluid is mainly derived from magmatic water with a small amount of metamorphic fluid. S isotope studies show that δ³⁴S of pyrite is between −2.52‰ and 2.61‰, which is within the composition range of meteorite S, reflecting that the sulfur in the deposit mainly comes from deep mantle, which may be related to magmatic activity. The pyrite ²⁰⁶Pb/²⁰⁴Pb ranges from 18.0314 to 18.2503, the ²⁰⁷Pb/²⁰⁴Pb ranges from 15.5907 to 15.7308, and the ²⁰⁸Pb/²⁰⁴Pb ranges from 38.1726 to 38.4326, indicating that Pb is mainly derived from magmas, and to a lesser extent, the Cambrian-Ordovician strata. Combined with the geological characteristics, fluid inclusions and H-O-S-Pb isotope research results, as well as the regional tectonic evolution background, it can be concluded that the Saibagou gold deposit is an orogenic gold deposit formed by continental collision between the Qaidam Block and Olongbuk Block and its genesis is closely related to the dike activities in the mining area.