The flow pattern at the entrance area of the approach channel of navigation junction under the by-pass layout form is mainly influenced by the connecting river’s morphology.Taking Guangxi Yongning hydraulic junction project layout scheme at feasibility study stage as a study case,we prob into the relationship between the flow pattern at the entrance area of the upper & lower approach channel of the junction under the by-pass layout form and the main stream,we also study the improvement measures for the navigation flow condition.Constructing the diversion dike at the lock’s entrance area and excavating the right-bank shoal,we solve the problem of great backflow at the upper approach channel’s entrance area of Yongning junction;Adjusting the lower-stream left-bank excavation line,we solve the problem of serious backflow due to the large angle between the main flow direction at the lower approach channel’s entrance area and lock’s central line,so that we can ensure favorable navigation condition at the entrance areas of both the upper and lower approach channels.