In order to scientifically and objectively evaluate the level of modernization of water conservancy development in northern Jiangsu Province, on the basis of the index system of water conservancy modernization of Jiangsu Province, the TOPSIS method based on the weight of the variation coefficient was used to calculate the weights of current evaluation indices. In comprehensive consideration of the weights of the current evaluation indices and the evaluation indices of water conservancy modernization of Jiangsu Province, the indices were weighted again, in order to comprehensively evaluate the water conservancy modernization of six typical counties in northern Jiangsu Province and to verify the rationality of the method. The study results show that the index system with new weights thoroughly reflects the characteristics of northern Jiangsu Province and meets the region’s development requirements, and it is closely related with the present situation of water conservancy development in northern Jiangsu Province, providing guidance for the water conservancy modernization in this region.