Abstract: Through the observation and analysis of Well Ming D2, it is proposed that the slumping deepwater gravity flow sediments are widely developed with various sedimentary structures and obvious characteristics in Cretaceous Nantun Formation and Damoguaihe Formation in Dongming sag, Hailaer Basin. Based on sedimentary process, the simplified classification scheme represented by Shanmugam is used to divide the slumping deepwater gravity flow into four processes, i.e., sliding, slumping, debris flow and turbidity current. Meanwhile, this paper describes the sedimentary characteristics in each stage of the process, summarizes the main identification marks, analyzes and discusses the formation mechanism. It is considered that the three stages of sliding, slumping and debris flow of the slumping deepwater gravity flow are dominated by the mass flow transport mechanism, and the sedimentation in the stage of turbidity current is mainly controlled by Newtonian fluid or turbulent flow mechanism. In the sliding stage, the partial reservation of primary sedimentary structure characteristics, such as sand-mud interbed and sedimentary cycle, is mainly identified by the development of small normal fault or reverse fault in internal layers, and large stratigraphic dip. The sediment in the slumping stage is mainly characterized and identified by plastic deformation with the top and bottom abruptly contacted with dark mudstone, as well as the large-scale internally-developed syndepositional soft-sediment deformation structures, such as convolute structure. The debris flow can be classified into sandy and muddy debris flows. The debris flow sediment is mainly marked by the Bingham fluid and overall frozen sediment with the top and bottom of sandstone abruptly contacted with dark mudstone, massive sandstone as well as the favorable conditions for developing floating gravel and mudstone tearing clastics. In addition, the reverse graded bedding can be developed in the sandy debris flow. The turbidity sediment transported by Newtonian fluid is mainly indicated by normal grading bedding, the bottom abruptly contacted with dark mudstone, and the development of complete or incomplete Bouma sequence.