From the perspective of the rainfall input of a model, ridge estimation is introduced based on differential response rainfall error estimation, to solve the problems of multicollinearity and instability of least square estimation in runoff error correction based on dynamic system response curve. The optimal ridge coefficient is synthetically determined by trial and construction, then the discharge is corrected by rainfall error estimation. The method is applied in both the ideal case and the Qilijie basin for inspection. The results indicate that: ridge estimation of rainfall error based on differential response is the error correction method of flood forecasting, it can improve the accuracy and stability of flood forecasting which has obvious correction effects, which is worthy of further popularization and application in the future.