Previous studies on Sanmenxia Reservoir mostly have been focused on the interannual degradation and aggradation changes, while there were few studies on the erosion and deposition distributions of the reservoir area during flood/non flood seasons. Identifying the erosion/deposition centers (sub-reach with greatest adjustment rates during flood/non flood seasons), the migration of erosion/deposition centers in the reservoir area and their rates and influences to the changes of the riverbed elevations at Tongguan during flood/non flood seasons were analyzed based on the data of water discharges, sediment loads, and erosion/deposition volumes after the controlled releases of “storing the clear water during the non-flood seasons and discharging the turbid water during flood seasons” in the period of 1974-2018. Results showed that the reservoir was generally degraded during the flood seasons and aggraded during the non flood seasons, and the erosion/deposition centers generally migrated correspondingly. The erosion/deposition centers had migrated downstream with an average rate of about 1-2 km/a at 90 km away from the dam before 2010 and then moved upstream at 60-70 km in front of the dam in 2018 with significantly weakened erosion/deposition rates. There is a strong positive correlation between the river kilometer (RKM) of the erosion center from the dam and the 2-year exponential weighted average value of flow energy during the flood seasons. So did the RKM of the deposition center and the backwater length with 5-year exponential weighted average value. The riverbed elevations of Tongguan are negatively correlated with the bed slope of Tongguan-Tai'an Reach which means the greater the gradient, the lower the riverbed elevation of Tongguan. The channel slope of Tongguan-Tai'an Reach increased easily and the riverbed elevation of Tongguan decreased when the erosion center was located at the downstream of the Tongguan-Tai'an Reach. When Tongguan was out of the backwater area and the erosion/deposition centers were also located below the Tongguan-Tai'an Reach after 1985. During this time, the riverbed elevations of Tongguan had been less affected by the erosion/deposition centers.