This paper uses an indoor modeling test and simulates the sliding and accumulation process of landslide debris avalanches. Then, the paper acquires and further analyzes the deposit position of each granule of landslide-debris avalanches. In addition, this paper briefly analyzes the motion mechanism of landslide-debris avalanches. The result shows the follows. The deposit position of the slide-debris is of both randomness and regularity. These particles that are symmetrical on the central axis of slope board are still symmetrical after the slide. The deposit position of these granules in consecutive region previously is not continuous after the slide. The deposit position of the particles is affected by its initial positon conspicuously. The inside holistic rolling of slide-debris is founded in the process of slide. The result of the experiment provides reliable reference for the research of motion mechanism of landslide-debris and for backtracking the initial state of slopes.