Water conservancy modernization(WCM)forms an important part of the national modernization. To make the evaluation of WCM be more scientific and reasonable, an evaluation index system consisting of seven sub systems and twenty seven indices is established, including flood control and waterlogged reduction, water resources guarantee, water environment and ecological protection, rural water project guarantee, urban drainage and supply, water management service and water conservancy development guarantee. A cloud model(CM), which has both fuzziness and randomness is used for the evaluation. The CM determines the comprehensive evaluation index weight by using backward and forward cloud generator, and calculates the rank by condition cloudgenerator. The paper uses set pair analysis as a comparative analysis(SPA). A case study is put forward with XinyiCity of Jiangsu province. The results show that, the evaluation values are 85. 53(CM)and 84. 56(SPA)in 2015 and the level of WCM in Xinyi City is basic modernization, consistent with the actual situation. In 2020, the evaluation values are 93. 71(CM)and 91. 38(SPA), both can achieve the level of comprehensive modernization, consistent with the 13^th Five-Year Plan. The effectiveness and applicability of the CM is verified.