This paper analyzes the hydraulic problems in discharge capacity，energy dissipation and navigation flow condition after the layout of Tangba navigation-power junction in mountainous river. Then，based on the physical model ，the hydraulic problems such as the low energy-dissipation rate of bottom flow， the increase of tailrace water level and poor navigation flow condition are analyzed and optimized，and the measures such as changing the form and scale of stilling basin，excavating the riverbed，expanding the diaphragm wall and blocking water to navigation are put forward，which effectively improve the flow conditions and ensure the normal operation of the navigation-power junction.