Abstract: The hydrological regime of Dongting Lake is affected by the Yangtze River and other four water inlets around the Dongting lake. The refill operation of the Three Gorges Reservoir（TGR）has a great impact on the water level of the outlet of Dongting Lake. In this paper, the water level simulation model is used to simulate the water level process of the outlet of Dongting Lake to quantify the influence of the Three Gorges Reservoir refill operation. The daily out flow rate of the Three Gorges Reservoir and the synthetic daily flow of other four water inlets around the Dongting Lake is the input and the daily water level of Chenglingji hydrological station（outlet of Dongting Lake）is output. In order to find out the Chenglingji hydrological station water level change process of returned to original condition that the Three Gorges Project is not carried out daily out flow rate of the Three Gorges Reservoir been replaced by the daily in flow rate. The out flow of the Three Gorges according to the calculate of different refill operation are used to substitute for measured daily out flow rate of the Three Gorges Reservoir as the input data to simulate the water level change process under the different operation. The influence of water level in Chenglingji hydrological station under different operation are been compared and the results proves that: The water refill operation have a great impact on the water level of the Chenglingji station. The earlier time refill operations have a longtime influence and the average water level change is relatively large, but the water level process is relatively gentle. In the other hand, the earlier ones have a shorter time influence and the overall average water level changes is small, but the water level process is more dramatic. Different years and types of water source should be taken into account so the water level process needs the specific analysis and discussion