The navigable flow condition in the upstream approach channel of the second-line shiplock of Mengzhouba hydro-junction is studied by means of overall fixed-bed model experiment and ship model navigation test.According to the results,the transverse velocity at the anchor segment and the entrance area exceeds the standard under the engineering arrangement of the original design scheme,which does not meet the specification requirements of the navigation flow condition.By extending the length of the diversion wall and setting permeable partition at the bottom of the wall，the engineering arrangement is optimized and a recommended scheme is proposed.Under the recommended scheme,the navigable flow condition at the entrance area is improved significantly,and the ship maneuvering parameters are controlled within limits of requirements.It indicates that the ships can pass through the entrance area safely.