Abstract: Qintong Sag is a downfaulted lacustrine basin with strike-slip faulting. With the sequence stratigraphy theory and method, stratigraphic framework of the first member of Funing Formation has been established, and two types of depositional system have been discerned, including delta system and lacustrine depositional system. Then based on analysis of sand content and seismic attributes, depositional systems of lowstand system tract, expanding system tract and highstand system tract of the first member of Funing Formation have been recovered, and this research shows that the characteristics of time-space distribution of these three system tracts have certain inheritance and discrepancy. Comprehensive studies suggests that, in Qintong Sag, Yinzhuang-Guangshan area has developed large delta depositional system in the depositional period of lowstand system tract, dominated by mouth bar and sheet sand, and these two types of sandbody can be good reservoirs;Huagang-Beihanzhuang area of the west slope belt has developed large scale delta depositional system in the depositional period of lowstand system tract and highstand system tract, dominated by plain channels and mouth bar of delta front, and this type of sand also can be good petroleum reservoir.