Abstract: The shales developed in continental rifted lacustrine basins in the eastern part of China have shown promising potential of shale oil exploration. However, influenced by multi-provenance inputs, these shales exhibit complex lithofacies and significant heterogeneity in shale oil accumulation. Therefore, we investigated the 3rd lower sub-member of Shahejie Formation in the Gubei Sag, Bohai Bay Basin, to unravel the developmental patterns of shale lithofacies under multi-provenance condition, elucidate differential shale oil enrichment in different lithofacies, and thereby evaluate the resource potential. Key findings reveal that in the ternary discrimination of carbonate, felsic, and clayey terminals for shale lithofacies, the clay-rich hybrid lithofacies exhibits optimal oil content due to high organic matter abundance, dominance of Type I kerogen, well-developed micropore-fracture network formed by oriented arrangement of illite/smectite mixed layers, and high hydrocarbon retention efficiency. The carbonate-rich and felsic-rich hybrid lithofacies display moderate oil content. In contrast, the felsic-carbonate lithofacies, despite possessing the highest brittleness index, shows the lowest organic matter abundance and oil content. Reservoir spaces in different lithofacies are dominated by micron-scale dissolution pores, inter-crystalline pores, and clay interlayer fractures. Importantly, the predominant orientation of high-conductivity fractures aligns with the present maximum horizontal principal stress, which significantly enhanced the potential for generating complex fracture networks during hydraulic fracturing. Comprehensive analysis of crude oil properties (light-medium oil) and over-pressured zone distribution identified that the eastern subsag and northern central uplift in the study area are the “sweet spots” of shale oil accumulation. This study provided a guidance to the exploration deployment in the Gubei Sag with theoretical insights for shale oil exploration in similar continental rift lacustrine basins with strong multi-provenance inputs.