Abstract: To assess impact of ecological water replenishment on streamflow in the Yongding River basin, temporal and spatial changes of streamflow from 1961-2018 and changes before and after ecological water compensation were analyzed．Annual streamflow has shown a significant decreasing trend with change point of 1983．After the change point year, the average annual streamflow decreased significantly, the daily stream flow duration curve showed that the distribution duration of low streamflow increased, the difference of daily runoff of the year became larger．After large-scale ecological water replenishment, annual inflow of Guanting Reservoir has significantly increased compared with average years before, monthly flow process has an obvious bimodal process, satisfaction rate of ecological flow has significantly increased. Ecological water replenishment has played a positive role in streamflow under current conditions．