Due to the limitation of temporary wharf at the entrance of harbor basin，the navigable width at the entrance does not meet the requirements of the large ships entering and leaving the harbor basin. According to the ship maneuvering simulation test results and correlation analysis，we know that the flow velocity and wind force outside the entrance of the basin have great influences on the trajectories of towing ships entering and leaving the basin. When the flow velocity outside the entrance is not more than 0.45 m/s and the wind force is not more than force 6，the ship can safely enter and leave the harbor basin. The theoretical analysis and experimental research reveal that when the calculation result of navigable width does not meet the specification requirements，the purpose of safe entry and exit of ships can be achieved by means of auxiliary operation of tugs and limiting boundary conditions such as wind，wave and flow.