After a careful study on background, the change of mineralization degree in the lake was determined. The results simulated show that the water of the lake, with a mineralization degree of 1900 mg/L, will be unlikely changed into fresh water even after more than 100-year power station running. There are 53 genera of phytoplankton and 42 genera of zooplankton in the lake, characterized by species diversity and the lack of biomass as other oligotrophic lakes. It is predicted that the change of water temperature and nutrient is not great, so the impact on the characteristics of plankton and fish can be negligible. After developing the power station, the impact on terrestrial ecosystem is expected to be not great. But the temperature in summer will increase by 0.2~0.4℃, a benefit to some crops. Besides, the new beach abandoned by water is favourable for the development of stock-raising and agricuture. Finally, the remedial measures for ecological environment have been devised in case unfavourable impact occurs.