Abstract: The Cenozoic strata of Yinggehai Basin is rich in natural gas, and exploration breakthroughs have been achieved in the middle and deep strata of the basin in recent years. The discovery of gas fields in the Ledong 10 area had attracted concerning for the migration and accumulation of natural gas in lithologic reservoirs in the middle and deep strata of nondiapir structures. The natural gas reservoir in the Miocene Huangliu Formation in the Ledong 10 block appeared to have a high content of CO₂. The characteristics and periods of CO₂ migration to natural gas reservoirs were discussed by the approaches including Laser Raman spectroscopy and combined with inclusion petrographic observation. Five types of fluid inclusions were classified, including brine inclusions, CO₂ inclusions, gas-phase CH₄ inclusions, gas-mixed inclusions and gas-mixed brine inclusions. According to the homogenization temperature and density of CO₂ inclusions measured by Laser Raman and microthermometry analysis, and combined with the estimation of the capture conditions of CO₂ inclusions, sedimentary characteristics, burial history as well as isotopic composition of CO₂, two-stage filling mode for CO₂ gas reservoirs was then concluded. The first stage was high-density inorganic-origin CO₂ charged between 1.4-0.9 Ma; the second stage was medium-density inorganic CO₂ charged between 0.7-0.4 Ma.