Abstract: The Mouru Gold Metallogenic Belt is one of the three major one in the Jiaodong Gold Metallogenic Zone. The Jinqingding Gold Deposit is located in the southern part of the metallogenic belt and is a large quartz vein-type gold one. The research on its ore-forming fluid is still controversial. This paper starts from the study of fluid inclusions and H-O isotopes in ore quartz, combined with the geological characteristics of the deposit to discuss the ore-forming fluid and ore-forming process. Petrographic study on fluid inclusions in ore quartz showed that the primary inclusions were mainly two-phase gas-liquid inclusions and pure liquid-phase aqueous solution inclusions, with a small amount of CO₂ three-phase inclusions. Microthermometric results and calculations showed that the homogenization temperature was mainly between 188.7 and 252.1 ℃, the salinity was mainly between 4.23% and 10.71%, the density was concentrated between 0.87 and 0.99 g/cm³, the ore-forming pressure was mainly between 48.9 and 67.3 MPa, and the ore-forming depth was between 5.6 and 6.63 km. With the ore-forming process, the temperature, pressure gradually decreased, and the density gradually increased. H-O isotope tests showed that δD values were mainly between -96.0‰ and -83.2‰, and δ¹⁸O values were mainly between 3.06‰ and 5.58‰. The ore-forming fluid was mainly derived from the mixture of magmatic and metamorphic water, and the cooling and non-mixing of the fluid were the main mechanisms for the large-scale precipitation of ore-forming materials in a short time. It is concluded that the Jinqingding gold deposit should belong to the hydrothermal vein-type gold deposit with characteristics of medium-low temperature, low salinity, low density and medium-shallow formation.