Abstract: In order to improve the accuracy of real-time flood forecasting, the unit hydrograph was introduced to the real-time flood forecast updating system. The error feedback updating model tracing the source of information was established. In this paper, the details of the model structure and principles were described, and the ideal model was set to test the efficiency of the updating system. The correct results of different error ranges were compared. The results indicated that the efficiency of the updating system was improved, and the proposed method with simple structure, clear physical concept, and the forecast lead period is not lost. Conclusively, the proposed method could be widely applied in real-time flood forecast updating.