To explore the potential evaluating methods of regional sponge city under the context of urban flood, this paper establishes the potential indicator system of sponge city from the perspectives of rainfall, water pollution, flood disaster and ecological green land. Because these four elements are closely related with sponge city. Taking the national-level Tianfu District as an example, the regional index system is studied comprehensively by using the methods of mathematical statistics, fuzzy neural network, fuzzy synthetic evaluation and satellite image recognition; besides, the construction potential of Tianfu District sponge city is evaluated with the methods of gray correlation analysis quantitatively; moreover, the potential index ranking of every sponge city in every district and county is given. Finally, a new drainage system is developed according to flood disaster. The results show that it is relatively objective to evaluate the sponge city potential from the above four aspects, namely, rainfall, water pollution, flood disaster and ecological green land; also, the indicator vector of Shuangliu Area has the minimum correlation with the ideal indicator vector, which means this area is the most proper and potential place to carry out the sponge city construction in Tianfu District; furthermore, the developed underground drainage system can alleviate problems of city waterlogging, water quality and pipe network pressure and so on. The mentioned evaluating methods of the potential of sponge city and the developed underground drainage system can provide references for promoting the construction of sponge city.