Abstract: Xiangxi River is the biggest tributary of the Three Gorges Reservoir in Hubei Province, which has a length of 94 km, a catchment area of 3 099 km² and a natural fall of 1 540 m. There are many small run-of-river dams in the Xiangxi River system because of the high natural fall and their environmental consequences are worth paying more attention. From 20 October to 1 November in 2005, 18 small run-of river dam related segments were selected for measuring the main physicochemical variables and chlorophyll a concentrations (as a proxy of ecosystem function). The result showed that: (1) the main stream and the four tributaries demonstrated a high spatial heterogeneity in terms of environmental variables; (2) apparent impacts of cascade small run-of-river dams on chlorophyll a concentrations were found, particularly for the site just below the intake dam, where chlorophyll a concentrations increased significantly; (3) for the whole catchment, the main drivers of ecosystem function were DO, water depth, turbidity and flow velocity, however, different responses were found in distinct tributaries, indicating the potential effects of spatial heterogeneity; (4) almost 50% of the investigated river sections were dried out during the sampling period, and this implies that it’s urgent to quantify the minimum ecological water requirement to mitigate the negative effects of these dams. In addition, we advocate that understanding the interaction between run-of-river dams and other multiple stressors and their consequences on river biodiversity, ecosystem functions and services will be a core topic in river ecology, since this is essential for sustainable river basin management.