The organization relationships of government investment in public projects are complicated, with many participation subjects. In order to reduce project risk, cut loss and control costs, this paper based on the risk management and the whole life cycle management theory to carry out research. Firstly, the risk events in each stage of public project identification, risk factors and the subject analysis. Through the construction of the system for the whole process of risk management of public welfare projects, and the use of fault tree analysis (FTA) method for qualitative and quantitative analysis on the whole process of risk. Research shows that during the whole life cycle of public welfare project, the external environment of the project, planning unreasonable, improper operation management, project improper maintenance, the owner mismanagement and other factors are the main factor, which lead to the government investment project risk events. Based on this, we puts forward the corresponding risk response measures; at the same time provide more information for the government investment decision-making.