Abstract: Although freshwater ecosystem service flow regarding supply and demand has attracted wide attentions, few studies have considered the influence of water quality regulation service on fresh water provision service flow. The watersheds of southeastern Fujian are disturbed by human activities and typical water scarcity have been caused by pollution. Based on supply-demand analysis, InVEST model and scenario analysis were used to quantify ecosystem services supply, demand, and flows within Huashan Creek Watershed in Pinghe County, where freshwater ecosystem services are strongly affected by the intensive agricultural activities. The interactions of freshwater provision services (water quantity) and regulation services (water quality, taking nitrogen pollution as example) and their impacts on freshwater ecosystem services flow were addressed both at watershed scale (i.e., the natural status) and political scale (i.e., the proposed status). The results show that (1) In the context of watershed scale, the ecosystem services flows were 4.59×10⁸ m³, and decreased to 9.9×10⁷ m³ under nitrogen pollution stress with the reduction rate of 78.43%, while the paths of flow were not affected. (2) In the context of political scale (i.e., the proposed status), the dynamic flows of freshwater ecosystem services were about 4.63×10⁷ m³, and decreased to 4.02×10⁷ m³ considering water regulation services, with a reduction of 13.17%. Water quality have changed the supply and demand of ecosystem services, and subsequently altered the path of flows, which switched Xiazhai County from supplier to beneficiary. The results of the study could be references to the researches on ecosystem services flows and provide guidelines for regional/local water resources management.