On the basis of detailed observation of petrography, and this study defined the types, periods and compositions of fluid inclusions in the volcanic rocks of the Yingcheng Formation in Songliao basin, using the characteristics of fluid inclusion, homogenization temperature, gas composition and carbon isotopes. In addition, the poolforming periods of volcanic gas reservoirs with a high content of CO2 were analyzed. Integrated geological and geochemical evidence shows that hydrocarbon accumulation features in the volcanic CO2bearing reservoir in Songliao basin contain two accumulation periods characterized by successive recharging process, i.e., sedimentary period of QuantouQingshankou formations and the middlelate stage of Nenjiang Formation deposition. CO2 was recharged in the Himalaya period, later than hydrocarbon gas.