The PPP water conservancy project is of long project cycle, large investment and high risk characteristics. Based on the idea of fuzzy mathematics, the evaluation model for option of PPP water conservancy projects is established under fuzzy condition, and the fuzzy option value of projects under staged construction and the change of the whole project value under fuzzy decision-making condition are quantitatively evaluated. Combined with case analysis, the key influence factors of the fuzzy option value are found, and it is emphasized that the implementation of PPP water conservancy projects should focus on the management of cash flow value. The results will help the government and social capital to fully understand the project value, and actively participate in the implementation of projects and reasonably response to potential uncertain factors.