Abstract: Basing on the field exploration and laboratory experiment on the Zhengguangou debris flow in Helan mountain of Ningxia, the geo-environmental background of the debris flow formation has been summarized in this paper, the terrain trigger condition and run-off generation and accumulation mechanism have been analyzed. On the basis above, the characteristics values of kinematics and dynamics have been calculated, and the risk degree has been assessed further. The result indicates that the Zhengguangou debris flow should be a turbulent debris flow, with the mean density of 1.73 t/m³ and the triggered critical slope of 16°(or tanθ ≥ 0.29). Besides, through the calculation of mean flow velocity (4.08m/s), flow (98.14m³/s), single maximum flow volume (2.38×10⁴m³) and other factors, the Zhengguangou debris flow could be considered as moderately dangerous, with the risk degree of 0.397.