According to the measured data after impoundment and operation of the Three Gorges Reservoir, the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research results achieved in the demonstration stage. It is indicated through analysis that the reservoir sediment deposition and downstream river channel scouring during 8-year impoundment and operation are still within the original forecast, so the original forecasting results are feasible. The further observation and comparison should be conducted because the comparison between the observed data and the original forecast is not so sufficient in time and the prototype observation and related research work should be strengthened in the future.