Abstract: Surface flow erosion is one of the key geological disasters for oil and gas pipelines crossing alluvial fans. In this paper, the UML model was established using the CASE tool provided by ArcGIS to assess the risks of surface flow erosion to oil and gas pipelines crossing alluvial fans in respect of six index factors at hazard points, i.e., anti-scourability, permeability, angle of repose, water flow rate, slope, and angles between pipeline and channel. The database of oil and gas pipelines crossing alluvial fans was created by using this model. By means of buffer analysis, Kriging interpolation method and overlay analysis, the ultimate grid map was divided into five classes according to natural breakpoint method, and the risk level of the buffer was defined. The study results are consistent with actual pipeline conditions obtained through investigation. Therefore, this study provides a new idea for risk assessment on the surface flow erosion of oil and gas pipelines crossing alluvial fans.