Haigou gold deposit is a typical orogenic gold deposit． There are a reasonable amount of fluid inclu- sions in the gold deposit， including three types: CO₂ -H₂O- NaCl inclusions， pure CO₂ inclusions and NaCl- H₂O inclusions，of which most of them are CO₂ -bearing inclusions． The fluid salinity is 1.43% -9.08%，mainly concentrated in the range of 4.69%-5.41%，the density of CO 2 is 0.69 -0.80 g/cm³ ，indicating that the mineralization fluid is low- medium salinity and low density fluid． A series of studies on gold- bearing quartz vein and fluid inclusions show that there exists a positive correlation between the degree of the gold mi- neralization and the amount of CO₂ in the inclusions，which means the more CO₂ - bearing inclusions there are，the higher the content of gold is． CO₂ is mainly derived from mantle fluid，and the ore- forming fluid should be derived from mantle fluid and the crust shallow fluid． The conclusions have important denotative meaning on the metal- logenic mechanism of orogenic gold deposit and the deep prospecting on metal deposit．