Abstarct: In recent decades, with the growing evidences of climate change, concerns over the planning and exploitation of water resources have increased in response to these new conditions. An increase in these concerns has led to many studies in assessing the severity of the adverse effects of climate change on water resources. The variation in the amount of runoff entering the reservoirs of hydroelectric dams is one of the adverse consequences. baxsed on recent reports, about 16 percent of the world's electricity generation, and also 70 percent of the world's renewable electricity, comes from hydroelectric power. The huge benefits of hydroelectric power generation, including its very low cost and near-zero greenhouse gas emissions, have made this a popular source of energy throughout the world. Therefore, the assessment of the vulnerability of hydroelectric power generation systems is essential in the face of the consequences of climate change. In this study, Bakhtiari dam basin and its hydroelectric reservoir system have been investigated and the effect of climate change consequences on hydropower energy expected from hydropower plant has been evaluated. In order to consider probable uncertainties, two climatic scenarios were used. Then by using a statistical method and using the SDSM4.2 software, the large scale data obtained from the implementation of the CANESM2 general circulation model under the two scenarios RCP4.5 and RCP8.5, and under the short time horizon of 2020-2040, are microscopic and According to the HEC-HMS rainfall-run model, the amount of runoff entering the reservoir of Bakhtiari dam was calculated. Then, by developing a comprehensive water resource planning model for the whole basin, the effects of climate change on the inflow into the reservoir and subsequent production of Bakhtiari hydroelectric power were studied under both scenarios. By examining the overall results of the research, it can be seen that in this horizon the reduction in the energy produced by the hydroelectric power plant is significantly reduced in both scenarios. Therefore, updating reservoir operating rules and considering the consequences of climate change is a good way to reduce the adverse effects of climate change.