Because of the special flow structure in the entrance area of the approach channel of the hub ship lock，the sediment deposition in the entrance area is still an important problem affecting the normal operation of the river ship lock. According to the structural characteristics of the three-dimensional flow in the entrance area of the approach channel of the hub ship lock，a complete three-dimensional non hydrostatic mathematical model which can simulate the flow structure in this area with high efficiency and high precision is developed. The characteristics of its flow structure are analyzed and studied. From the perspective of eliminating the backflow and the navigation flow in the return gate area，the engineering measures that can effectively slow down the sediment deposition in the gate area of the approach channel are put forward，so as to provide technical support for the improvement of the navigation energy of the hub and the safe and efficient operation of ships.