Water management issue is recognized as one of the main concerns of climate change due to an increasing level of drought in terms of its magnitude and severity. This paper tries to prioritize water management-related climate change adaptation policies based on a probabilistic CBA (Cost-Benefit Analysis) approach. First, we classify adaptation policies into four types and evaluate the BCR (Benefit-Cost Ratio) of each type. Second, the risk premium of each adaptation policy type is evaluated, and the BCR is reestimated after taking risk premium results into consideration. Lastly, we found that the estimated probabilistic distribution function of the BCR revealed a remarkable result: “the economically feasible adaptation policy type evaluated at an average can be economically unviable with a probability of 29.38% (RCP 8.5).” In conclusion, the estimated results show that the BCR is hardly over unity, and the priority of adaptation policy can be different when uncertainty effects of climate change associated with extreme weather events are taken into consideration.