The lower lock approach of Mashi lock extension project is located on the right bank of Rongjiang River and bent to main flow,flood thrust obliquely channel so that the navigation condition in the entrance area is very complex.We put forward three optimized layout schemes by these measures,such as planning the deviation of the route to the right bank,arranging the breakwater,increasing the diversion pier and rotating the axial angle of the diversion pier.Using numerical simulation of whole two-dimensional flow model of Mashi hydro-junction,we analyze and compare navigation flow condition in entrance area of every optimized layout schemes,and obtained the better scheme which can meet all navigation safety index.