Abstract: There are a series of oil-and gas-bearing reservoirs in Qijia-Gulong Sag in Songliao Basin,including Fuyu,Gaotaizi,Putaohua,Heidimiao,etc.The characteristics of these reservoirs were discussed according to the homogenization temperatures of reservoir inclusions and micro-Fourier transform infrared spectroscopic analysis combining thermal evolution histories of the reservoirs.The types and characteristics of the organic inclusions indicate that there are 3 main migration periods of oil and gas generated from K₁q¹ source rock.There are different pool-forming periods for different reservoirs,and the oil/gas properties of reservoirs are the comprehensive reflection of multi-period pool-forming processes.The homogenization temperatures of inclusions show that the 3 pool-forming periods of the oil and gas in the sag are in the ends of K₁n,K and E respectively.The pool-forming periods are well consistent with the tectonic-developing history in the basin.