By using the historical data of the Three Gorges Reservoir (TGR), a flood forecasting model for TGR intervening basin was proposed and established, with which the quantitative precipitation predicted data was coupled to study the influence of flood forecasting accuracy. A stochastic precipitation generator was developed to generate 500 precipitation series as the inputsof proposed flood forecasting model. The mean values of the forecasted discharges were used as the final forecasted results. It showed that the proposed flood forecasting model coupled with the stochastic precipitation generator could increase the TGR flood forecasting precision.