Floods in the upper reaches of Tuojing River belong to the typical model purely natural characteristics. Adopting the history flood the series, analyzing the El Nino phenomenon with sunspot activity as the influence to the flood, through analysis of the regulation of the period change and various mathematic statistics methods of analysis forecasts, the paper provided the synthetical analysis for each kind of and related factors influenced to the annual maximum discharge in upper reaches of Tuojing River of Sanhuangmiao gauging station. It increased the accuracy of the long-term flood forecasting in upper reaches of Tuojiang River.