Abstract: In order to explore the risk of debris flow under different rainfall scenarios, the researchers in this paper took Yaokangba gully in Yala Township of Kangding City in Sichuan Province as the research object to evaluate the potential risk of debris flow under four rainfall conditions. Firstly, the numerical simulation method was used to reproduce the whole process of debris flow dynamic evolution, and the model was calibrated to complete the risk zoning of the study area. Then, a vulnerability evaluation model was constructed based on the quantitative relationship between the damage characteristics of buildings and the depth of debris flow. Finally, the refined quantitative risk assessment of Mengqing Village in the outlet of Yaokangba gully was realized, through the coupling of risk and vulnerability assessment. The results showed that under the rainfall frequency of 20%, 5%, 2% and 1%, the maximum flow velocity of Yaokangba gully debris flow was 6.2 m/s, 7.0 m/s, 7.7 m/s and 8.3 m/s respectively, and the maximum flow depth was 6.7 m, 7.2 m, 8.0 m and 8.8 m respectively. When the rainfall frequency decreased from 5%, 2% to 1%, the number of buildings threatened by debris flow increased to 8, 10 and 12 respectively. The area of high-risk area increased significantly from 2.463×10³ m² to 4.689×10³ m² under 20% and 5% rainfall frequency. The research results could provide scientific basis for geological disasters and risk control in Yala Township.