This paper analyses the assessment current situation of the hydropower station water-saving and power-increasing capacity with different regulating performance in the Hanjiang river upstream basin, puts forward two concepts of assessment index: water consumption for power generation and water energy utilization rate, defines the relevant calculating parameters of water-saving and power-increasing capacity of daily regulating performance of hydropower station, and establishes the water power calculation process of water-saving and power-increasing capacity. Data analysis and validation of the study are carried out through practical application of Xihe Hydropower Station on Hanjiang River. The results show that the assessment method of water-saving and power-increasing capacity of hydropower station based on the daily regulation performance is reasonable and feasible.