Abstract: To improve the accuracy and stability of the real-time flood forecasting, a new error correction method is introduced. The new method is based on another named runoff error correction based on dynamic system response curve(DSRC). And it is named as runoff error proportionality coefficient correction method based on system response (REPC). In this method, calculated runoff series is divided into some shorter ones according to certain principle. System errors are assumed to occur in each series, and the errors can be expressed by a proportionality coefficient. The proportionality coefficient can be estimated by choosing the appropriate parameters of the model derived from the system response. REPC method, as well as DSRC method, is applied in Tankeng basin. The results indicate that both methods can improve the accuracy of the real-time flood forecasting, but REPC method performs better results with regard to the accuracy, the stability and the range. With the sound physical laws and the long forecasting, the method introduced in this paper is well worthy of further applications.