Abstract: For lack of 3D seismic data and logging data, the previous research of sedimentary facies in the Bohai sea sag were not detailed enough for fine reservoir description. Based on the latest high-resolution three-dimensional seismic data, we carried out the high-resolution well-seismic sequence analysis and seismic sedimentology research for the Lower Ed₂ of Dongying Formation in the BZ3-8 Block, western slope of Bozhong Sag. Results show that on the north and the south sides of the study area, there occurred different sediment provenance systems and facies. During LST and HST periods, fan-shaped and flower-shaped seismic multi-attributes and amplitude anomalies dominated in the northern part of the study area, indicating fan-delta deposits, while northeast banded seismic multi-attributes and amplitude anomalies were found in the southern part of the study area, that was interpreted as the braided-river delta deposits. During the TST period with the rapid rise in lake level, small-scale fan deltas remained in the north. The sedimentary facies evolution of the system tracts of the sequence of Lower Ed₂, from LST (rich sand), TST (rich mud) to HST (rich sand), reflects a classical distribution pattern of stratigraphic lithofacies in a sequence stratigraphic framework, which is significant to reservoir and source rock prediction.