Due to serious sediment deposition in the upper reaches of Wudingmen sluice in the outer Qinhuai River in Nanjing, a physical model was established and two schemes were designed to study the silt reduction effect of a diversion wall with a 15°deflection angle in the upstream of the sluice. In scheme 1, a scope of 60 m upstream of the sluice was excavated to the design section. After two years and eight months of flow and sediment process, the sediment volume in the regulated section was reduced by 30. 4% after the diversion wall configuration. In scheme 2, a scope of 240 m upstream of the sluice was excavated to the design section also with a diversion wall. The sediment volume of the regulated section was reduced by 50. 8% and 44. 0% after one and two typical hydrological years respectively. The range of sediment reduction decreased, the riverbed tended to form a new balance between erosion and deposition, and the topography of the section tended to show a uniform distribution. The results show that the diversion wall with a 15°deflection angle can significantly reduce the siltation in the upstream of the Wudingmen sluice and can improve the flow capacity of the channel.