With the continuous rapid growth of freight volume of Changzhou Hub in recent years,the four existing locks can no longer meet the increasing requirements of freight volume crossing,and the fifth-line lock need to be built to meet the needs of freight volume development.Based on the method of integral hydraulic model test,this paper studies the navigation flow condition in the entrance area of downstream approach channel of Changzhou fifth-line ship lock,and it puts forward the measures to improve the navigation conditions of the downstream approach channel.The results show that,affected by the unconnected riverbed topography in the entrance area of the downstream approach channel of the fifth-line ship lock,the oblique flushing of the discharge flow from Waijiang River and the jacking of the convex nozzle in the downstream bend,there are bad flow patterns such as large cross flow and backflow in the entrance area,and the navigable flow conditions are poor.By adoption of measures such as adjusting the river bottom elevation of the downstream connection section of the entrance area,removing the downstream curve convex,dredging and expanding the beach on the left bank of the Waijiang River,which can effectively improve the navigation flow conditions in the entrance area of the five-line ship lock,and adjust the routes of ships entering and leaving the lock,so as to meet the safety navigation requirements of ships.