Abstract: Based on the time series analysis and the optimization control theory,this paper propses the water level forecasting model with backwater effect,which basically overcomes the shortages of not directly dealing with backwater effect in hydrologic way and complicated calculation in hydraulics way.For prismatic cannel the constraint condition of paramenters of the model is geven.The water level forecasting of the Jinjiang Reach of the Yangtze River with backwater effect is well solved by the model.