Abstract: The improvement of flood forecasting accuracy is crucial for disaster prevention and mitigation in river basins, and error correction is the key to improving flood forecasting accuracy. Focusing on Yong′an River in Zhejiang Province, using the system differential response error correction method, the feedback correction of runoff error is constructed through the calculation of water sources, slope confluence, and river confluence systems in the Xin′an River model. The model was calibrated and validated using 17 floods from 2001 to 2023. After correction, the relative error of peak flow rate decreased from 6.2% to 4.6%, and the average coefficient of certainty increased from 0.915 to 0.940. During the validation period, the relative error of peak flow rate decreased from 7.1% to 2.9%, and the average coefficient of certainty increased from 0.934 to 0.959. Research has shown that the system differential response correction method can significantly improve the accuracy of flood forecasting in the Yong′an River Basin and has good application effects.