The sedimentary characteristics of the Fuyu oil layer in the Toutai area of the Songliao basin show a transition from meandering-delta to lacustrine deposition. The sedimentary environment evolved from delta plain to delta front to shallow lacustrine, indicating a deepening water body during deposition. The distributary channel microfacies of the meandering-delta are well-developed, with sandstone being a favorable reservoir. The presence of good storage-seal assemblage, formed by muddy rock enveloping distributary channel sand, mouth bar, and thin sand layers, creates favorable conditions for lithologic trap hydrocarbon reservoirs.