坡面流作用下的颗粒侵蚀不仅导致严重的水土流失，同时也可能诱发严重的重力地质灾害如滑坡、泥石流等。研究其发生发展的机理以及内部理论规律对减灾防灾具有至关重要的作用。以水动力学公式为基础，从坡面颗粒侵蚀的水分环境角度入手，分析了浸泡状态下松散颗粒和固定颗粒的侵蚀机理，揭示坡面水流与坡面颗粒间的相互作用关系，给出各类型侵蚀发生所对应的临界条件。最后，通过实例计算验证了理论的合理性。

The slope particles erosion under slope flow not only causes the serious soil erosion, but also the heavily gravity disaster, such as landslides and debris flows. So studying the internal mechanism of the erosion becomes a very important problem in disaster reduction and prevention project. In the article, on the basis of the formula of water dynamics and the view point of particles water environment on slope surface, the erosion mechanism of slope particles has been studied. Then, by analyzing the relationship between overland flow and slope erosion, the critical conditions of erosion for different kinds of particles are given. Finally, an example is given to prove the theory.