Ecosystem Services (ESs) are continuously supplied by ecosystem to meet human’s demand and benefit human society. The supply-demand relationship of ESs has become a hot topic in ES studies, but there still lack a full chain analysis from supply to benefit, and it’s hard to reflect ES’s actual contribution to human society in a comprehensive way. Taking water purification service (WPS) as an example, this study proposed an evaluation method of the benefit of ecosystem services integrating supply and beneficiaries from the perspective of spatial flow, and carried out a case study in the Taihu Lake Basin. The results showed that the supply of WPS decreased from 5.55×10⁷ kg to 4.55×10⁷ kg during 2000-2020, with a decrease rate of 17.97%. The amount of beneficiaries, however, increased from 2.69×10⁹ person to 3.90×10⁹ person, increasing by 45.19%. This continuously increasing demand for WPS finally led to a 25.35% increase in the benefits of WPS from 2000 to 2020 in the Taihu Lake Basin. The result also showed the beneficiaries would be underestimated if the spatial flow was neglected, and a considerable difference exists between ‘potential’ and ‘actual’ benefit of WPS. Finally, this paper divided the Taihu Lake Basin into eight sub-basins based on supply, beneficiaries and benefit, and proposed corresponding governance suggestions for the improvement of WPS in the Taihu Lake Basin.

Ecosystem services; Water purification; Spatial flow; Beneficiaries; Taihu Lake Basin