Eco-hydrological regulation service is an important component of ecosystem services, which can effectively regulate surface runoff and alleviate rainstorm-flood disasters. However, due to the expansion of urban construction, the degradation of the ecological environment, and the frequent occurrence of extreme precipitation, the spatial imbalance between the supply and demand of eco-hydrological regulation services has emerged. This phenomenon was exacerbated by the weak terrain hydrodynamic force and high demand for urban development in plain cities. In this study, from the perspective of the supply and demand of ecosystem services, we used the runoff regulation capacity to characterize the supply level of eco-hydrological regulation services and expressed the demand level of eco-hydrological regulation services by the risk of rainstorm-flood disasters, to construct a research framework on the supply and demand of eco-hydrological regulation services in plain cities. Therefore, we took Tianjin as an example to evaluate the supply and demand level and their spatial distribution characteristics of eco-hydrological regulation services based on the SWAT model, random forest model, and ArcGIS platform, and then we used the matching degree of supply and demand to divide the research unit into four types. Finally, we used the priority index to divide these areas into five planning intervention priorities. The results showed that:(1) the supply capacity exhibited a feature that the distribution was high in the southeast coastal area and low in the northwest mountainous area. The distribution of demand levels presented a multicenter aggregation and gradually decreases from the center to the outside. (2) There was a positive correlation between supply and demand spatial distributions. Low supply-low demand dominated four types of supply and demand matching, which had the most obviously spatial aggregation. (3) There were obviously spatial variations in planning intervention zones. The priority intervention area was consistent with the urban built-up area distribution, accounting for 5.41% of all the planning intervention zones. Such areas were mainly concentrated in the central city, followed by the core area of Tianjin Binhai New Area, which was the focus of future planning and governance. The results provided a scientific basis for urban planning management to prevent and control rainstorm-flood disasters in plain cities according to the supply-demand relationship of the eco-hydrological regulation service theory.