The discussion of sedimentary macrostructures of debris flows and their formation mechanism ns based on the data of the process and deposition of the present and ancient debris-flows in Dongchuan of Yunnan, Wudu of Gansu and Fuxin of Liaoning. Non-cohesive debris flow with a density of 1. 3 - 1. 7 T/m3 follows the hydraulic fluid or granular flow model. In the hydraulic fluid of flood, electrolytic water combines with clay to form pulp transporting solid debris. The sedimentary structures showing fluid processes are stone-line structure, imbricated structure, gravel supporting-superimposed structure. A part of non-cohesive debris flow and transitional be-bris flow (density 1. 7 - 1. 9 T/m3) follow the granular flow model. Debris is subjected to the actions of friction, collision and dispersion, of which dispersion action forces coarse debris moving upward to form inverse graded load, The sedimentary structures showing granular flow include inverse graded bedding, inverse-normal graded bedding, imbricated-vertical structure, and circling linear structure. Cohesive debris flow with a density of 1. 9-2. 3 T/m3 follows the structural two-phase flow (viscoplastic) model. The sedimentary structures showing the processes of cohesive debris flow are inverse graded-chaotic structure, bottom mud-chaotic structure, and out-wedging structure.