By use of the method of simulating laboratory-rainfall, the paper got the relationship between rainfall, slope and export coefficients of TN and TP of in the upstream watershed of Xin'an river. It then calibrated and verified the export coefficient of TN and TP through the experiment of runoff plots under the condition of natural rainfall so as to obtain the model of improved export coefficient. With the help of ArcGIS software, the paper got the area, rainfall and slope which was needed for model application. Based on the improvement model of export coefficient, it estimated export loads of TN in and TP in tea garden of red-soil of upstream watershed of Xinanjiang.The results showed that the pollution loads of TN and TP are 3618.72 kg/a and 521.17 kg/a respectively on the tea garden of red-soil in the upstream watershed of Xin'an river.