Abstract: As an important part of the urban ecosystem, water bodies is an crucial part of the systematic and whole-area promotion of sponge city construction. In order to explore the relationship between the urban water surface rate and the risk of flooding, the dynamic monitoring of the water body area in the central urban area of Suqian City of Jiangsu province in 2023 was carried out through GPS-RTK and GIS remote sensing technology, to analyse the factors affecting the change of the water body rate, and to study the relationship between urban flooding and the water surface rate by establishing the computing grid zoning as well as the different drainage zoning, combining the urban flood-prone points with the water surface rate. The results show that: The water body area in the central urban region of Suqian city was 31.824 km² in December 2023, which increased by 0.047% compared with 2022. Among the natural and anthropogenic causes of changes in the water body rate, human factors are dominant, and measures such as water systems connectivity and ecological restoration in sponge city construction are important means to enhance the water bady rate. The analysis of waterlogging points and water body rate shows that water body rate is one of the factors affecting urban waterlogging, and waterlogging is more likely to occur in areas with lower water body rate. The research results are of great significance to the systematic and comprehensive promotion of sponge city construction in the whole region.