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The Rushan gold deposit, formerly called Jinqingding gold deposit, is Currently the largest lode gold deposit in terms of single vein gold resources. It is located in the middle part of the Muping-Rushan gold belt in the Jiaodong Peninsula, China. Gold occurs mainly in pyrite-and polymetallic sulfide-quartz vein/veinlet stockworks. Fluid inclusions in the altered wallrocks and gold ores contain C-O-H fluids of two main types, namely CO2-H2O arid H2O-rich. Quartz in the alteration zone including slightly altered granite, K-feldspar-quartz rocks and sericite-quartz rocks contains abundant CO2-H2O inclusions, whereas in gold sulfide ores CO2-H2O inclusion abundance decreases gradually. Microthermometric data show the homogenization temperatures of the CO2-H2O inclusions in the alteration zone fall in the range of 236 - 377 degrees C; homogenization temperatures, obtained mainly from type I-C and type 11 inclusions in the pyrite quartz vein arid polymetallic-sulphide quartz vein, range from 170 degrees C to 324 degrees C. The initial auriferous fluids were CO2-dominant (X-CO2 reach to 0.53) with salinities from 3.33 wt% to 10. 48 wt% NaCl equiv. These fluids, modified by fluid/ rock reactions with altered wallrocks, were gradually evolved into H2O-rich fluid with minor CO2 (X-CO2 = 0.01 similar to 0.05) arid aqueous fluid in the main ore-forming stage. Its salinities range from 1.23 wt% to 12.55 wt% NaCl equiv. Co-occurrence of gold and sulfides (especially pyrite) suggests that gold was transported most likely in the form of gold sulfide complex in the Rushan deposit. The wide distribution of CO, inclusions suggests that the pH variation during gold transportation was controlled by CO, buffering. Fluid/rock reactions and fluid immiscibility, resulted from cooling arid depressurization, possibly led to the gold precipitation.