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Based on core data, microphotographs, well-logging and test analysis, etc., combined with regional geological data, the characteristics of mixed rocks in oil group I of the upper third member of the Paleogone Shahejie Formation in the Dawangzhuang area, Raoyang Sag, Bohai Bay Basin, were studied. The sedimentary environment was analyzed, and the sedimentary model was explored. The study shows that the mixed rocks may be divided into two categories: siliciclastic carbonate rocks and carbonate siliciclastic rocks. Mainly sandy dolomite and calcareous sandstone occur in the Dawangzhuang area, with mainly siliciclastic carbonate rocks in the central and northern areas, and carbonate siliciclastic rocks in the west and south. The genetic types of mixed sedimentation are dominated by facies mixing in the early and middle stage of oil group I of the upper third member of the Paleogone Shahejie Formation oil group, and by in situ mixing in the early stage of oil group I of the upper third member of the Paleogone Shahejie Formation oil group. A few cases of source mixing were found in the late stage of oil group I of the upper third member of the Paleogone Shahejie Formation oil group in the study area. The sedimentary environment of the mixed sedimentation of carbonates is mainly shore-shallow lake in the Dawangzhuang area, classified into three kinds of mixed deposits: sandstone bar microfacies, carbonate bar microfacies, and muddy shore-shallow lake microfacies. A comprehensive analysis of the effect of lake level variation on mixed deposition, together with tectonic evolution and paleogeo-morphology, revealed a sedimentary model of mixed rocks during steadily rising, then falling, lake levels. When the lake level was slowly rising, the mixed deposits characterized by both facies mixing and in situ mixing gradually increased. When the lake level was suitable, the content of pure carbonate rocks increased and facies mixing decreased. Later, when the lake level was falling, source mixing was evident. [ABSTRACT FROM AUTHOR]