According to the planning，the section from Longxikou to Yibin in Minjiang River will reach Grade III inland waterway standard through waterway regulation. According to the historical data，the 95% flow rate of the section over the years can only reach 662 m3/s. However，with the construction of large hydropower stations such as Zipingpu and Pubugou in the upper reaches of Minjiang River in recent years，the navigable flow of the reach has been greatly affected. Based on the runoff and sediment series of Gaochang hydrometric station before and after impoundment of Zipingpu Hydropower Station，we analyze the influence of Zipingpu and other large hydropower stations on the water and sediment characteristics of the river reach，and know that the amount of incoming sediment is obviously reduced，the annual distribution of runoff is homogenized，and the discharge is obviously increased in the dry season. Especially，when the multi-year guarantee rate is 95%，the discharge is increased by 166 m3/s and corresponding water level is increased by 0.21 m. The research results can provide flow support for the research reach to reach Grade III inland waterway standard.