The Songliao Basin is located in the Northeast China, where Daqing and Jilin oilfields were developed. At the period of the Member 4 of Quantou Formation of Lower Cretaceous in the southern Central Depression of the Songliao Basian, the basement subsided uniformly and slowly, and the topography of the basin was very flat, leading to the development of a delta at the setting of shallow water and a rapid rise in lake level. Base on studies of core, main facies markers and welllog facies,the reservoirs are mainly composed of lithic arkoses and feldspar litharenites. Three subfacies and nine microfacies were identified. The subfacies are delta plain, delta front and prodelta. The microfacies are distributary channels, levees, crevasse splays, interdistributary bays, subaqueous distributary channels, subaqueous crevasse splays, mouth bars, distal bars and subaqueous interdistributary bays. Delta plain and delta front were well developed, and prodelta was less developed. The distributary channel advanced toward the center of the lake over a long distance through filling deposition and branching channel frequently, and developed an obvious subaqueous distributary channel at the wide shallowwater delta front. The most oilrich reservoirs are compased of  channel sand bodies which had cut and oversfacked each other. The average width of single sand body is 200 to 600 meters and its thickness is 3 to 8 meters. This study is an important foundation for further oilfield production adjustment and development.