Abstract: Lock chamber size of Caojie shiplock on Jialingjiang River is 200.0 m×23.0 m×3.5 m(length×width×sill depth),the highest operating head is 26.7 m,the integrated hydraulic index of Caojie shiplock is top-ranked in the shiplocks that have been constructed in China.It is found from prototype debug that under condition of navigable water level 192.0 m,the water depth of the upstream approach channel is only 2.9 m during construction,the characteristics of unsteady flow in the upstream approach channel is obvious and there is a strong oblique flow and swirl near the floating type navigation wall,water surface gradient ratio and vertical velocity is high.It may endanger safe navigation of ships.In addition,a strong vortex will appear near the intake upstream when discharge is up to a certain value because the submerged depth in the intake is quite small;in some severe cases,it will appear the throughout suction vortexes which affect safety of ship in the chamber.Through prototype debugging,special hydraulic problems in the upstream approach channel during construction have been solved and a mode of shiplock operaton have been determined,and so that ship safe navigation must be ensured in ship lock during construction.