In order to solve current issue about existing water conservancy public-private-partnership(PPP) project risk decision of the investors in the psychology and behavior of cognitive bias, fuzzy decision information and random risk, the PPP project risk sharing scheme model was put forward, which was based on the cloud theory and prospect theory. First, the characteristics of water conservancy project were analyzed, and along with the investigation of construction site, the index system of risk sharing decision-making was established. Second, risk sharing index reviews of the cloud model were established through improved cloud model generation algorithm and the cloud distance and cloud possible degree were put forward, cloud foreground value function was obtained by cloud theory and prospect theory. Finally, the optimal weight of each risk sharing index was calculated based on the deviation maximization method, the fuzzy synthesis algorithm was used to synthesize the index weight and the cloud foreground value, and then the optimal risk sharing plan was selected. The results show that the decision-making method of water conservancy PPP project risk sharing scheme can quantify the uncertain decision information, which can improve the comparability of options and make decision-making more intuitive and clear.