Flood forecasting in the near-dam area of reservoir is challenging, and the accuracy of forecasting scheme usually cannot fulfill the requirements of flood prevention and scheduling. To address these problems, the entire near-dam area of Wuqiangxi Reservoir was divided into ten subbasins based on the distribution of historical rainfall centers and the characteristics of runoff generation and concentration. A new forecasting scheme was constructed using the three-source Xin’anjiang model, the model parameters were calibrated and the main causes of simulation errors were investigated based on typical flood events. The results show that the method proposed in this study can achieve the high accuracy of flood forecasting and is well applied in the real-time flood forecasting operation in 2021. The results also indicate that the lack of information on flood releases from water conservancy projects is the main cause of errors in runoff and peak flows.