Forthe problem that the rehabilitation degree of dangerous reservoirs is difficult to be accurately evaluated, a two-layer index system was established. The fuzzy gray clustering and combination weighting method are combined to quantitatively evaluate the rehabilitation degree of reservoirs. Firstly, the subjective and objective weights of each evaluation index are calculated by entropy method and analytic hierarchy process, and a combination weight containing subjective and objective implications is obtained using the combination weighting method. Secondly, the gray clustering method is used to evaluate the rehabilitation degree of each rehabilitation type. The clustering coefficient of each rehabilitation type is adopted to create the fuzzy evaluation matrix, and then the weight of each rehabilitation type is calculated. Finally, the comprehensive evaluation method is utilized to accurately assess the rehabilitation degree of dangerous reservoirs after reinforcing. The method is applied to the reinforcement assessment of three reservoirs in Henan and Jiangxi Province and the results agree well with the practical situation of the reinforcement assessment and the acceptance conclusions, indicating a great value in engineering applications.