The main flow in the downstream of the narrow and deep channel with sharp turn is inclined to the downstream of concave bank，and approach channel is arranged on the same side of the existing downstream junction，which makes some problems that the upstream approach channel occupies a large flow area and the velocity index exceeds the standard seriously. We study the layout and navigable flow conditions of the upper approach channel of second ship lock at the downstream junction of the sharp turn of a narrow and deep channel by the fixed river bed model and ship model tests. The results show that due to the influence of the sharp turn at the upstream junction of the narrow and deep river and the partition wall of the long approach channel occupying the thalweg，the navigation flow conditions in the entrance area of the approach channel on the lock in the design scheme are poor，which cannot satisfy the requirements of the safe navigation of ships. Based on the original design scheme，the optimization scheme sets a single downstream submarine dike，optimizes the excavation scope and type of the right bank，changes the length and sets holes of the separation wall，improves the navigable flow conditions of the entrance area considering the flood discharge capacity and power generation of junction，and achieves safe navigation of ships and normal operation of the hydro-junction.