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Sarekoubu gold deposit occurs in metamor- phosed acid volcanic rocks and volcaniclastic rocks of Devo- nian Kangbutiebao Formation along the southern margin of Altai Mountains in Xinjiang, West China. Pyritization, silici- fication and carbonatization are developed in wallrocks, and main gold mineralization stages are pyrite-quartz stage (Ⅱ) and polymetallic sulfide stage (Ⅲ). Primary fluid inclusions are often seen in main gold mineralization stages, which are almost pure CO2 liquid inclusions (LCO2) under room tem- perature with high densities of 0.85—1.07 g/cm3. CO2-rich inclusions (LCO2-LH2O) and H2O-rich inclusions (LH2O-LCO2) are subordinate. Fluid inclusions in stage Ⅰ (polymetallic sulfide stage) are more complex than in stage Ⅱ, containing CO2-CH4 system with ?78.1—?61.9℃of solid CO2 melting temperatures and ?33.7—?17.7℃ of partial homogenization temperatures. The trapping pressures of high densities are estimated to be 150—350 MPa. Laser Raman microprobe was used to confirm the composition of pure CO2 liquid in- clusions. δ C values of CO2 inclusions range from ?10.73‰ 13 to ?21.15‰, which are similar to some of fluids in the man- tle-derived minerals that contain surface organic carbon by subduction recycling. These characteristics differ from many hydrothermal gold deposits. CO2 fluids have a regiona source related to post-collisional orogeny.