To evaluate the comprehensive capacity of the water network in the Jianghai Plain, a typical area of Nantong City’s water network is taken as the research object, and an evaluation index system covering four aspects:water security guarantee, water resource regulation, water ecological support, and social coordinated development is constructed. The subjective objective collaborative weighting method was used to determine the weights, and the comprehensive capacity of the water network was quantified from three dimensions:structure, function, and efficiency. The obstacle degree of the evaluation indicators was calculated, and the key limiting factors were identified. The results show that the comprehensive capacity of the water network in Nantong City exhibits a spatial differentiation feature of strong in the south and weak in the north. Jiulyu Area has the highest score