For over 10 years of operation, the reservoir of the Three Gorges Project has retained ~75.5% of upstream sediment and disrupted the natural shape of the original waterway and the relative balance of water-sediment condition. The downstream waterway of the Three Gorges Dam has been intensively scoured, causing significant river-bed armoring. In this study, based on the measured terrain and bed sediment gradation data of the Yichang–Zhicheng river reach, the theoretical equation for incipient motion of non-uniform particles was adopted to calculate and analyze the bed sediment armoring and ultimate scouring depth of this river reach. Using 40,000 m³/s as the representative flow rate for calculations, the calculated ultimate scouring depth was close to the actual scouring depth from 2003 to 2010, indicating that this calculation method is reliable. If the Three Gorges Reservoir is operated following the designed scheme, i.e. the flood regulation and storage capacity is increased from the 45,000 m³/s to 55,000 m³/s, and 50,000 m³/s is used as the representative flow rate for calculation, then scouring will continue to occur in this river reach, and the average scouring depth will exceed 1.0 m; the scouring depth in the Yi47 section with relatively fine bed sediment particles will be above 2.0 m.