Abstract: Based on the application of laser raman microprobe analysis in situ technique, the nature of oil and gas inclusions in the 8^th member of the Shihezi formation in western Sulige gas field was identified. The composition and relative molar fraction of phaseⅡhydrocarbon-bearing organic inclusions in the healing fracture of the quartz grain surface and in the secondary enlargement margin were determined. The results show that the early-stage inclusions mainly are gas-liquid two-phase organic inclusions containing gaseous hydrocarbon and brine gaseous hydrocarbon, and the late-stage inclusions are gas-liquid two-phase organic inclusions containing gaseous hydrocarbon; The gas phase is dominated by gases such as CO₂, CH₄ and N₂, and the CO, H₂S, H₂, C₂H₂, C₂H₄, C₂H₆, C₄H₆, H₂O and CO₂are dissolved in it; the liquid phase mainly is consist of H₂O and CO₂, and also contains a very small amount of anion SO₄^2- and CO₃^2-(less than 0.03 mol/L). The research makes clear that the early-stage organic inclusions contain large amounts of CO₂, H₂O and a small amount of inorganic gas of low carbon alkane. It indicates that the early maturity of organic matter was in immature-low mature stage. Although natural gas is generated, the migration is limited in scale. The organic inclusions are few and far between. It reflects the replacement of formation water by natural gas entering reservoir. The late-stage organic inclusions are the opposite. The content of hydrocarbons and N₂ are higher, but the content of CO₂, inorganic gas and H₂O are lower. It represents the characteristics of the peak of oil and gas formation and large-scale oil and gas accumulation. It provides a scientific basis for the thermal evolution of organic matter, the generation and migration of oil and gas, and the division of oil and gas accumulation stages.