To ensure the basic navigation function of the channel during the construction phase of Lize Navigation-Power Junction，according to the results of the 1:100 normal fixed bed physical model test for the construction diversion and closure of Lize Navigation-power Junction，we analyze the navigable flow conditions and cofferdam closure test in the third stage of construction diversion period from the perspectives of velocity，flow pattern，navigable flow and navigation route，and obtain the calculation parameters of different closure widths.The results show that the test results obtained from the proposed diversion cofferdam scheme for the third phase of construction can well solve the navigation problem during the construction period of this navigation-power junction in terms of flow velocity，flow pattern and other water conditions.