The closed-type harbor is a new idea for the port construction in strong tidal and sandy estuary,and the key technical problems are the flow condition and sediment deposition in the approach channel.Taking the Shangyu closed-type port in Qiantang River estuary as an example,we analyze the flow condition and siltation intensity of the approach channel by empirical formula and numerical calculation.The results show that the flow condition of the approach channel at Shangyu closed-type port can basically satisfy the requirements of ships entering and leaving the port.The siltation intensity of the approach channel increases gradually from the navigation lock to the entrance area,and the siltation intensity near the entrance area is maximum.However,it decreases gradually from the entrance to the outside of the approach channel.The average siltation intensity of the approach channel is about 0.06 md.Jetting flow is adopted to raise the suspended silt at the bottom of the approach channel,and trench excavation in the leading dike of the approach channel is implemented to transport the suspended silt out of the approach channel.