Aiming at the problem that the poor visibility of the Three Gorges Project seriously affects the efficiency of gate-crossing,we use prototype observation method such as ship test to analyze the one-way controlled navigation maneuvering characteristics,and measure braking stroke data of the ship passing through the lock under fog condition.Referring to the empirical formulas of similar ship test applications,we calculate the braking stroke of representative ships,and analyze the minimum visibility requirement data corresponding to the required safe velocity in the lock water of the Three Gorges Project from a partial safety point of view.The results show that visibility of 200 m under fog condition can satisfy the requirement of controlled navigation in lock water,which can provide the references for further improving the passing capacity of the Three Gorges Project.