Abstract: The structure complexity of large-scale public projects leads to the complexity of the risk system,which is reflected in multiple risk factors, complex relations between risk factors and the larger impact of risk results. First,on the basis of the original definition of risk,this paper put forward the risk definition of large-scale public projects and analyzed its characteristics. Second,it unified index system from the nature of the project itself,project participants and the project environment. Finally,it determined the risk variables relationship in large-scale public project and made intuitive risk path diagram by structural analysis. Based on the research results,the paper divided the risk factors into four types by dependence graph,and proposed suggestions on risk management. The operability of the model was verified by example demonstration, which showed that this method could reduce the risk of the complexity of the system dimension and provide reference path basis for related risk management.