To counter the problems such as strong cross current and wide range of backflow at the downstream entrance area and connection segment of Jinggangshan navigation-power junction，we study the navigable flow conditions and optimization of the entrance area of the downstream approach channel of the navigation-power junction. Through establishing the overall fixed-bed model，we optimize the layout of the core wall，propose to shorten the core wall and add permeable core wall outwards the river center，so as to solve the problems such as strong cross flow and backflow，improve the navigation condition of the entrance area and connecting section of the lower approach channel notably，and meet the needs of safe navigation for the ship.