In the early period in operation of TGP, the navigation conditions in upstream approach channel of TGP lock will become more complicated because of the reservoir impoundment. When the reservoir water level is higher than the top of dividing dike, the navigation conditions change. According to this change, the navigation conditions in upstream approach channel have been studied by the hydraulic model test and remote - controlled ship model test. The study results show that in the navigation period the hydraulic parameters can meet the requirements of design in the entrance region and the approach channel, and the barge - tow model can navigate smoothly.