During the third phase diversion period of Longxikou Navigation-power Junction project in the Minjiang River,the ship lock arranged on the right bank will be used for temporary navigation.Due to the relatively low upstream water level,there is a large navigation risk in the entrance area and connecting section of the upstream approach channel of the lock under the condition of large flow in flood season.To ensure the navigation safety during the construction period,we carry out the numerical simulation study on the navigation conditions at the upstream of the ship lock under the lowest pool level in combination with the results of the diversion and navigation model test of the junction construction,and propose the engineering measures such as optimizing the left guide wall structure of the upper approach channel,reducing the excavation elevation of Jigongzui and filling the deep pool.The results indicate that the upstream navigation flow conditions are significantly improved,which can meet the navigation requirements during the construction period.