Abstract: Climate change has intensified the conflict between economic and ecological water demands, and brought challenges to the ecological operation of hydropower plants. This study examined the effect of climate change on hydropower generation and ecological operation of hydropower plants, and investigated the response of the interactions between power generation and ecological water demand to climate change. The hydropower operation model and the future streamflow projections modeled by climate projections of several global climate models are used. The downstream cascade of Lancang River hydropower plants was used as a case study. Results show that the overall streamflow and hydrological variability were predicted to increase under climate change, and the ecological flow destruction rate was also predicted to increase. The benefit of hydropower generation and its ecological effects varied more among different operational schemes than among different climate change scenarios, indicating that future conflicts between hydropower generation and ecological water demand are largely inevitable. The increase in hydrological variability caused by climate change can exacerbate the conflict between hydropower generation and ecological water demand, causing larger costs of ecological degradation when retaining the current hydropower benefits.