In order to explore the flow conditions of the approach channel shared by different levels of ship locks，we take Dayuandu double ship locks as an example,and use the method of combining 2-D flow mathematical model and physical model test to analyze the flow pattern,velocity distribution and unsteady flow characteristics of ship locks when delivering water in the case of different levels of ship locks are sharing the upstream and downstream approach channels.The results show that the layout of the common approach channel of the first and second locks of Dayuandu is feasible.The improvement measures for unfavorable water flow conditions in low probability conditions are proposed.The results of this paper can provide reference for similar ship lock projects.