With the latest river section data，we build a one-dimensional unsteady flow model of the Xiangjiaba-Luzhou reach，and analyze quantitatively the scheme of the minimum navigable flow and corresponding daily-regulated outflow for the Xiangjiaba Hydropower Station under ensured normal navigation during the impoundment period of the Baihetan Reservoir. Specifically，with assumed steady lateral inflow from Hengjiang River（70 m3/s）and Minjiang River（700 m3/s），we simulate the outflow from the Xiangjiaba Hydropower Station at different orders of magnitude and calculate the water level at each section along the way. The lowest navigable water level in the downstream below Xiangjiaba obtained is 265.8 m，and the corresponding flow is about 1 520 m3/s. Then，according to the daily peak shaving operation law of the station，the discharge flow is increased to a steady outflow of 1 700 m3/s during the day and reduced to 1 520 m3/s at night. As a result，the maximum water level variation is 0.31 m，which has little impact on the downstream ships. When the discharge flow is 1 700 m3/s，the width of 2.5 m water depth can be widened by about 20 m on that under the discharge flow of 1 520 m3/s. This method can alleviate the load reduction pressure on cross-dam transportation ships.