Abstract: This paper briefly introduces the hydraulics research results of TGP lock under all kinds of operational modes during the cofferdam retaining water, including the navigation conditions in the upper approach channel, the problems of supplementary water of lock chamber No.3 and overfilling or overemptying in lock chambers etc.. Some suggestions and concrete measures are raised for the optimum operation ways of locks and valves. Following these suggestions, the navigation of ships would be safe.