Abstract: This paper puts forward a quantitative risk assessment concept combined with numerical simulation analy? sis to address the risks of the high-speed railway tunnel project passing under an expressway. Firstly, a risk assessment index system is established by analyzing similar project experiences and taking into account the actual project context, and the overall system and inter-layer weights are ranked by the hierarchical analysis method. Secondly, on the basis of the numerical simulation results, a fuzzy comprehensive evaluation is made for the risk probability and consequences of the project, and the initial evaluation result of risks for the project is "moderate" risk. Finally, the corresponding risk control countermeasures are proposed for the main sources of risks, the risk reassessment is carried out according to the same procedure, and the result is "mild" risk, which indicates that the risk control measures are feasible and can provide guidance for the project.