Coordinating the relationship between economic development and ecological protection in the basin and alleviating the conflicts between upstream and downstream stakeholders through Payment for Ecosystem Services (PES) is a key measure to ensure the sustainable economic and social development of the basin. The key of the basin PES accounting lies in two points: firstly, how to simulate and quantify the flow direction, flow rate, flow velocity, and path of water supply and demand service flow for clarifying the supply and demand sides and their spatial relationship; Secondly, how to realize the raster scale-geographic unit-administrative unit scale derivation, to achieve the surplus, occupation, and spillover accounting of ecosystem services between different administrative units. In this study, we integrated various heterogeneous data sources, such as satellite remote sensing, economic and social statistics, and hydro-meteorological observations. We employed methods including water balance, water supply and demand service flow, and ecological value accounting. We constructed an accounting framework for horizontal PES standard in the basin based on water supply and demand flow and its spillover value accounting.; The flow direction, flow rate, flow velocity and path of water supply and demand service flow were simulated and quantified by using D8 flow direction method. The accounting of spillover value was realized from the spatial scale of "raster scale-topographic unit-administrative unit". Finally, we designed a scheme for collecting and distributing horizontal water PES funds in the basin. Taking Taihu Lake basin as an example, based on a comprehensive analysis of water resources spillover, occupation, and their values, the spatial and temporal relationship between water supply and demand, flow paths, and attribute characteristics at the county scale were analyzed. The responsible parties and payment targets were defined in combination with water quality indicators and a scheme for collecting and distributing payment funds was formed. The results showed that the boundary between water supply and demand in Taihu Lake basin was clear. The service flow was similar to the natural confluence process. The supply side was dominated by the western, southwestern and central counties of the basin, especially the western to central counties, which should receive more payment funds, and the average proportion of each county should receive funds over 2%/a, and Jiashan District, which should receive the most funds, had a proportion of more than 19.66%/a. The demand side gathered in the central and eastern parts of the basin, especially in the counties along the natural confluence of the Huangpu River, which should pay more payment funds, with the average proportion of funds payable by each county exceeding 5%/a, and the largest proportion payable was Pudong New District, with more than 15.48%/a. The net received payment funds basically showed the distribution characteristics of high in the west and low in the east, and most of the counties in the urban core area of the basin had negative net received funds. The accounting framework, quantitative accounting method, and fund coordination scheme of this study could be applied to the construction of horizontal PES mechanisms in other basins to achieve the overall coordination of ecological protection and economic development within and between basins.