Abstract: The “23•7” torrential rain triggered the largest flood disaster in the Haihe River basin since 1963, and led to numerous geological disasters, causing house damage, traffic disruption, and resulting in casualties and significant economic and property losses. The Mentougou District in Beijing has been severely affected by the disaster. Based on a detailed investigation of geological disasters after the torrential rain, this study counted a total of 353 new geological hazards in Mentougou District, including collapse, landslide, debris flow, and ground subsidence. The main contributing factors to the formation of geological hazards were analyzed, including heavy rainfall, intense slope erosion, inadequate drainage, slope cutting for construction, building on riverbanks or ditches, poor slope protection, loose and fractured rock and soil, and the accumulation of debris on slopes. Suggestions for hazards prevention and reduction in the construction of villages and towns have been proposed. These include following natural laws, restoring ecological space to rivers and ditches, and maximizing the buffering and ecological barrier functions of meandering rivers. Further emphasis should be placed on site selection and disaster risk assessment, along with improving the design quality and protective measures for geological disaster prevention projects. In similar Mountainous watersheds, it is necessary to strengthen the investigation, identification, risk assessment, early warning, and prevention of geological disasters to avoid the recurrence of such disasters in future rainstorm events.