Geological disasters are prevalent during urbanization in the mountainous areas of southwest China due to the complex geographic and fragile geologic conditions. This paper relies on the ArcGIS platform as the model operation carrier and takes Yiliang County of Yunnan Province as the research area. Nine evaluation factors such as slope and elevation were selected, and the risk assessment of geological disasters in Yiliang County is carried out by using the combination weighting method. The results show that: (1) the extremely high-risk areas and high-risk areas are distributed in the central, western, and northeastern parts of Yiliang County, of which 164 disaster points are distributed in the area, accounting for 72.56% of the total disaster points; (2) the elevation, human engineering activities, vegetation coverage, and distance from the river are the four main factors affecting the development of geological disasters in the area; (3) the proportions of extremely high-risk areas, high-risk areas, medium-risk areas, and low-risk areas in the total area of the county were 8.08%, 19.61%, 30.59%, and 41.72%, respectively; (4) the verification of the evaluation results by the receiver operating characteristic (ROC) curve shows that the evaluation accuracy is 80%, and the zoning results are consistent with the spatial and temporal distribution of historical disaster points. The combined weighting method can effectively evaluate the risk of geological disasters in Yiliang County, and the results can be used as a scientific reference for local government departments to carry out relevant work.