Based on the analysis of the Rao River waterway conditions and characteristics of the navigation-obstructing shoals,we establish a one-dimensional flow mathematical model to study the river section,which is verified by the measured data.By the mathematical model,we calculate the key parameters of the dredging depth channel in shallow shoal section and the variation of water line under the designed flow condition before and after the project,and analyze the changes of hydrodynamic conditions and the variation of flow velocity in section of the navigation channel.After the project,the water level and hydraulic gradient of the river section decreased.The average velocity of the navigation channel section in the shoal section of the lake area decreased,and the flow velocity of the lower reaches of the Shuanggang section increased.The annual back silting thickness of the navigation channel of shoals in the lake area after dredging of the navigation channel was calculated using the standard formula.The research results are available for reference by the design unit.