Abstract: The mountainous areas of Beijing exhibit a complex geological environment and are prone to frequent sudden geological hazards, posing significant threats to ecological security and to the safety of lives and property. This study aims to systematically analyze the spatial coupling relationships among geological hazards and their controlling factors—spanning geology, topography, and environmental conditions—and to develop a robust susceptibility assessment model to support regional disaster prevention, mitigation, and risk management. Based on the spatial distribution of 9,147 potential geological hazard sites in the mountainous regions of Beijing, nine influencing factors were selected from three dimensions—geological, geographic, and environmental: elevation, slope, aspect, curvature, distance to faults, distance to fold axes, stratigraphy, rainfall in 2024, and NDVI. An improved frequency ratio method was employed to develop the geological hazard susceptibility assessment model. The susceptibilities of collapse, landslide, and debris flow were comprehensively evaluated using the “maximum-value principle” (i.e., assigning the highest susceptibility class at each location). Factor intervals exhibiting strong positive correlations with hazard occurrence include elevation (150−450 m), slope (5°−28°), aspect (90°−270°), distance to faults (0−2,000 m), distance to fold axes (0−13,000 m), rainfall in 2024 (750−840 mm), and NDVI (0.38−0.85). The comprehensive susceptibility assessment results indicate that high-susceptibility zones covers 2,634.636 km², accounting for 26.08% of the total study area. These zones are mainly distributed around the Miyun Reservoir in central Miyun District, the southern and central-eastern parts of Huairou District, the piedmont areas of central Changping District, and the eastern parts of Mentougou and Fangshan Districts. Among the 37 geological hazard events recorded in 2024, 67.57% occurred within high- and relatively high-susceptibility zones, validating the predictive accuracy of the model. This study reveals the multi-factor coupling and complex response mechanism of "geological foundation−topographic manifestation−environmental triggering." The improved frequency ratio method effectively reduces the subjectivity in factor classification and the discontinuity inherent in the traditional method, significantly enhancing model discrimination capability. The results provide a scientific basis for geological disaster risk management in the mountainous areas of Beijing. High-susceptibility zones are concentrated around key ecological areas such as the Miyun Reservoir and southern Huairou, where disaster prevention and mitigation efforts should be prioritized, providing theoretical guidance for targeted geological disaster prevention measures.