A three-dimensional numerical model for debris flow was established with the particle discrete element method(DEM), and the movement characteristics of debris flow were analyzed from the full and local aspects. The results show that the movement process of debris flow can be divided into three stages, including starting acceleration, high-speed sliding, and reduced-speed deposit. When the bottom of the slope is flat, large particles are found on the surface of the deposition body, but small particles are in the middle and low areas. The velocity and energy loss of debris flow is significantly influenced by the contacts and collisions between particles. The maximum speeds of different parts of the debris flow are almost the same, and the time required to reach the speed peak is related to the initially horizontal position of particles, but not related to the deposit depth. Area division is distinct in the deposition body, and the particles of the deposition body are arranged according to their initially horizontal positions. The maximum deposit height is at the slope toe, and the deposit height gradually decreases towards both sides. Significant lateral movement occurs in the debris flow in the early and late stages, which can expand the scope of a disaster.