Built on the tail of Sanbanxi reservoir,Chengjing hydro-power plant generates electricity with the water head of Sanbanxi hydro-fluctuating,which can improve the flow condition of upstream as a result.The navigation lock is built among sluice gates.The flow condition of the approaching entrance area is significantly influenced by the operation scheme of the sluice.The downstream approaching entrance area locates at the convex of bank,and the flow condition is complex and cannot meet the demand of navigating safety.Focusing on the above questions,we probe into the causes of adverse flow regime with a scale 1:80 physical model.Taking measures including decreasing navigable standards,setting diversion piers,excavating the convex bank and optimizing the junction’s operating,we achieve the goal that the flow regime of the approach channel and the entrance area meet the demand of codes concerning the navigable flow.It provides a reliable basis for the hydro-power construction.