The second-line ship lock of Longtoushan hub is located in a slightly curved river section,and the downstream is affected by Longtoushan rock head,resulting in complex overall water flow conditions.The position of the ship lock is determined to be arranged by comparing advantages and disadvantages of the layout near the first-line ship lock and the layout near Gandong levee.The distance between the axis of the second-line ship lock and the axis of the first-line ship lock is determined by analyzing the cross-section of the lower ship lock head.Corresponding optimization measures are proposed by the physical model test.The results show that the position of the second-line ship lock is arranged near the first-line ship lock,and the distance between the axis of the second-line ship lock and the axis of the first-line ship lock is 100 m.Measures of the reconstruction and expansion of upstream and downstream baffle walls,as well as the dredging of the right bank beach downstream,can improve navigable conditions of the first-line ship lock and optimize the planar layout of the second-line ship lock.