To investigate the distributions and correlations of single-stage and multi-stage particles in debris flow accumulation areas, this paper utilized the approaches of onsite investigation, particle analysis, and statistical analysis, the feature of a debris flow accumulation area and its horizontal and vertical particle distributions were analyzed. The results show that: the debris flow accumulation area has a shape consisting of high center and low sides with identical lengths in the transverse and longitudinal axes; in the longitudinal direction, the grain size gradually increase from the outfall to the leading edge of the alluvial fan, the percentage of the curve range maximum grain size peaks at the central line and declines to both sides gradually, and the concentration of particle size is high in the central line; in the transverse direction, the grain size has an increased tendency from the outfall to the leading edge of the alluvial fan, the curve range maximum grain size increases, the percentage of the curve range maximum grain size grows steadily, and particle size concentration is high in the center; in the vertical direction, the layer thickness of accumulations grows from the top to the bottom gradually, the curve range peak grain size is mainly in the range of 10~20mm with a relatively high concentration. This study provides insight towards – the mechanisms of the debris-flow forming and also provides references for the prevention and control of debris flow.