Urban waterlogging disasters frequently occur in China in recent years, and “Seeing the Sea” is very common in the rainy season. However, there is no unified evaluation index system to assess the degree of urban intrusion. In order to get a more complete evaluation index system of waterlogging degree of sponge city, the concept of the momentum of waterlogging potential energy was introduced based on the dynamic duration characteristics of urban intrinsic temporality. The indexes system for the evaluation of urban intrinsic degree, including the local indicatory instantaneous index, the local indwelling comprehensive index, the regional overall indifference index standard value, and the corresponding calculation and analysis methods were established. The Zhongjiao Future City in Fenghua District of Ningbo City was taken as a case. The SWMM model was used to calculate the intrinsic conditions in the region. Results show that the calculated local indwelling comprehensive index can effectively reflect the degree of internal flaws and the internal flaw design of the city. The value could evaluate the degree of the city’s overall internality. The calculated average of the region’s overall internal level can describe the overall rationality of the flood prevention design of the LID (low-impact development) measures, and the index system can effectively reflect the spatial and temporal distribution characteristics of the internal plutonium. Adopting dimensionless quantity, the evaluation method is proved more scientific.