Based on daily streamflow data at 7 stations during 1956-2016 and daily precipitation data at 72 stations during 1960-2016 in the Huai River Basin (HRB), the eco-surplus and eco-deficit under influences of abrupt streamflow behaviors were analyzed using Flow Duration Curve (FDC). Regarding the relations between ecological indicators and hydrological alteration indicators, we analyzed the ecological effects of the altered hydrological processes. Besides, we also quantified fractional contributions of climatic indices to ecological flow using Generalized Additive Models for Location, Scale and Shape (GAMLSS) framework. The results indicated that: (1) the FDC was subject to general decrease due to hydrological alterations, and most streamflow components were lower than 25% FDC. We found the decreased eco-surplus and the increased eco-deficit due to altered hydrological processes. The FDC of the streamflow along the mainstream of the HRB was lower than that along the tributaries of the HRB. The changes of eco-surplus (eco-deficit) matched well those of precipitation anomalies. The hydrological regulations of water reservoirs acted as the major factor behind mismatch between summer ecological flow and precipitation anomalies. (2) Eco-deficit (eco-surplus) was increasing (decreasing) at annual and seasonal scales with exception of winter season. In winter, the eco-surplus was higher than other seasons. However, the eco-surplus was decreasing persistently. The 21^st century witnessed the lowest eco-surplus along the main streamflow of the HRB and Shannon index indicated the decreased ecological diversity across the HRB. (3) The ecological flow was highly sensitive to Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO) and Nino3.4. Meanwhile, the ecological flow along the main stream of the HRB was highly sensitive to climate indices. While the ecological flow by GAMLSS model had better performance in the fitting of extreme value and local trend.