Abstract: The regulation capability of the Longmentan Reservoir is poorer; after the first cascade hydropower station was put into operation, there was surplus water every year. The feasibility and the necessity of the capacity expansion were analyzed. Different reformation schemes for capacity expansion were compared, a reformation scheme was put forward, in which the turning wheel will be replaced by the new one, and an assistant generator will be added (two generators will be driven by one hydraulic turbine in one axial); and the favorable effect was obtained after the reformation. 

Key words: hydropower station, water resource, turning wheel, capacity expansion