Abstract: ObjectiveTo explore the refined vulnerability model of buildings in the mountainous areas of Southwest China under the threat of debris flow, Methodsthis study takes Zhao Yuanzigou in Hanyuan County, Sichuan Province as the research area, establishes a numerical model based on the dynamic process of debris flow, and uses the Massflow numerical simulation method to evaluate the risk of debris flow under different rainfall frequencies, and constructs the vulnerability model of masonry structure buildings, Finally, a set of quantitative risk assessment methods for debris flows based on the dynamic process of disasters was formed. ResultsThe following main conclusions are drawn: (1) The maximum flow velocities of debris flows under four different rainfall frequencies are 10.3 m/s, 11.3 m/s, 12.1 m/s, and 12.5 m/s respectively, and the maximum mud depths are 9 m, 13 m, 14 m, and 15 m; (2) When P=2%, the areas of extremely high and high-risk zones are 0.05×10⁴ m² and 0.8×10⁴ m² respectively, affecting 5 and 2 buildings. When P=1%, the area of extremely high and high-risk zones further increased to 0.11×10⁴ m² and 1.2×10⁴ m², affecting 6 and 5 buildings respectively. (3) Under the rainfall frequency of P=2% and P=1%, this settlement area has been completely covered by debris flows, forming a medium and high-risk area.ConclusionsThe above research results can provide reliable scientific basis and practical guidance for the precise prevention and control of debris flow risks in mountainous areas of Southwest China.