Abstract: The Kundeqi Nanshan gold deposit occurs in the north of Xiaoxinganling-Zhangguangcailing polymetal metallogenic belt, with orebodies hosted in the silicified arkose and fine sandstone of Cretaceous Guanghua Formation. The gold mineralization covers three stages, involving quartz-pyrite, quartz-polymetal sulfide and quartz-calcite. Research was carried out for the fluid inclusions in quartz from the silicified quartz vein ores of the former two stages, which include gas-liquid two-phase, gas-rich phase and daughter mineral-bearing three-phase, dominated by the gas-liquid two-phase. The homogenous temperature ranges from 234.8 to 420.5℃, with salinity (NaCl eq.) between 2.6% and 33.6%, which can be classified into high temperature-low salinity, medium-high temperature-low salinity and medium-high temperature medium-high salinity types. The gas compositions in fluid inclusion are mainly H₂O and CO₂. The liquid compositions are also dominated by H₂O and CO₂, with Na⁺, K⁺, Ca²⁺ and Mg²⁺ ions. Halite is the major daughter mineral. The three types of inclusions coexist in the same mineral grain, suggesting that the hosting fluid have been in inhomogeneous state, showing certain immiscibility during the ore-forming process. Based on the study result for the fluid inclusion, the deposit is decided to be epithermal genesis, with potentiality for porphyry type of mineralization in the deep.