According to the factors such as hub scheduling and artificial sand excavation after Xiaoxitan hydropower station is built,the characteristics of water and sediment,and river level and discharge are changed.Combined with the engineering arrangement of diversion embankment,we carry out the condition analysis and rechecking of the downstream navigation flow under the changing terrain conditions.Using numerical simulation method,we establish a numerical simulation model of two-dimensional hydrodynamic hub downstream,optimize diversion dike layout and the size parameters by numerical calculation and program results,and put forward the hub downstream approach channel of diversion dike layout suggestions,which can meet the requirements of the navigation flow conditions change terrain conditions.It also can reduce the influence of the original design scheme on the flood discharge capacity of the river.