Abstract: Debris flows pose a serious threaten to human safety and ecological stability due to their sudden onset and destructive power. Zhalong gully in Min County, Gansu Province, is prone to frequent debris flow events, highlighting the need for disaster prevention and early warning. Based on the FLO-2D numerical simulation model, rainfall intensity data with return periods of 10 a, 20 a, and 50 a were selected. Combined with a high-precision digital elevation model (DEM) and debris flow parameters determined by field investigation, the movement process of debris flow (flow velocity, flow depth, and range) under different rainfall return periods was simulated, and disaster risk zoning was conducted. Buildings, roads, and land within the affected area were selected for vulnerability assessment, and a risk zoning map was generated by combining the results with a risk assessment model. With the increase of rainfall intensity, the peak flow, flow velocity, and flow depth of debris flow increased significantly, and the hazard was the highest under the 50 a return period rainfall. High-risk areas were concentrated in downstream accumulation zones, and the increase in rainfall intensity raised the risk for buildings in low-risk areas. The results of this study are of great significance for debris flow disaster prevention, early warning, and risk management, and provide a foundation for subsequent research on precise and quantitative risk assessment methods.