The Xiaomiaoshan gold deposit in Dingyuan County of Anhui Province is a typical quartz vein type gold deposit in the central southern part of Zhangbaling uplift adjacent to the Tan-Lu fault belt in the west. Gold mineralization mainly occurs in NNE-extending quartz veins in the peripheral contact zone of Guandian-Wawuliu adamellite and subordinately exists as sparse disseminations in altered rocks. Petrographic studies reveal four types of primary fluid inclusions in quartz veins sampled from the Xiaomiaoshan gold deposit, i.e., vapor-rich, liquid-rich, CO2-bearing and daughter minerals-bearing fluid inclusions. Fluid and stable isotopic geochemical methods, such as microthermometry, laser Raman microprobe, bulk composition and H-O isotopic analysis of fluid inclusions, were used to investigate physicochemical properties, chemical composition and sources of the ore-forming fluids so as to probe into the metallogenic mechanism of this type of ore deposits. The homogenization temperatures of these fluid inclusions range from 133℃ to 378℃, with the peak values being in the ranges of 180℃～200℃ and 220℃～260℃. The calculated salinities［w (NaCl)］ range from 0.2% to 44.6% with the peak values between 3% and 6%. Four types of fluid inclusions coexist in the sample; the vapor-rich fluid was homogenized to a single vapor phase, while at the similar temperature range, the liquid-rich fluid was homogenized to a single liquid phase. These phenomena indicate that the boiling process might have played an important role at the ore-forming stage. According to homogenization temperatures, salinities and vapor-liquid ratios, the fluid pressures were estimated to be 4 to 13 GPa, 23 and 60 GPa, respectively, suggesting that gold mineralization took place over 6.5 km in depth. Based on the laser Raman analysis of the fluid inclusions, it is found that the gas composition is mainly CO2, H2O vapor with a tiny amount of CH4. Group analyses of fluid inclusions indicate that the liquid phase mainly contains Na+, K+, Ca2+, F-, Cl-, NO3- and SO42-, while the gaseous phase consists of CO2, N2, H2O, CH4, C2H2 and C2H6. The K+/Na+ ratios vary between 1.55 and 2.75, and F-/Cl- ratios are between 0.02 and 0.03. δ18OH2O values of the fluids trapped in the quartz vein range from -2.39‰ to 2.14‰, and δDH2O from -512‰ to -45.9‰, respectively. The isotopic characteristics indicate that the ore-forming fluids were mostly derived from the magma and mixed with the meteoric water at the late stage. Through integrating geological settings with physiochemical properties and isotopic geochemistry of the ore-forming fluids in the Xiaomiaoshan gold deposit, it is concluded that the NS-trending faults constituted themigration pathways of the ore-forming fluids and places of gold precipitation. When the fluids of high temperature and high salinity were mixed with meteoric water along the fracture zone, the oxygen fugacity increased and the temperature, salinity and pressure decreased remarkably, which caused the disassociation of the gold complexes and resulted in gold precipitation.