Abstract: In order to reduce the PPP(Public Private Partnership)project implementation risks and improve the risk prevention of government and private investors, so that it can make more profitable decisions, reduced investment losses, achieve mutual benefit and win-win situation as well. Therefore, this paper take PPP project preparation stage venture as research target to identify and confirm four types of risks.At the same time, using fault tree analysis(FTA)to evaluate the risk factors that belong to different part, and quantify risk impact base on risk identification. In addition,it determine the important order of risk factors on PPP project preparation stage by calculating unit structure importance.The result shows that accuracy of government decision-making, rationality of private investors funds allocation and instability of market returns is the main factor that generate projects total risk.