针对降雨输入不确定性对实时洪水预报影响的问题,本文采用不考虑未来预报降雨、考虑未来预报降雨、考虑预报降雨的降雨量误差和降雨时间误差4种方法,以陕西省两个半湿润流域(陈河流域和大河坝流域)为研究区域,分析不同预见期和不同降雨输入情况下洪水预报的精度.研究表明:相对于不考虑未来降雨情况,考虑未来降雨后在预报预见期较长时对预报结果精度提升较大,在预见期较短时对预报结果精度提升不显著;暴雨中心位置不同对预报精度影响也不同,当暴雨中心位于流域下游时降雨量误差对流量预报误差影响更大;降雨量误差主要影响洪量相对误差和洪峰相对误差,且这种影响是线性的,对确定性系数的影响是非线性的二次函数,降雨时间误差主要影响峰现时间误差.;In this paper, the characteristics of flood forecasting by Xin'anjiang model were studied in Chenhe Basin and Daheba Basin, in order to solve the problem of rainfall uncertainty in real-time flood forecasting. Four methods, namely considering forecasting precipitation, discarding forecasting precipitation, adding rainfall forecasting error and adding rainfall time error, are applied to analyze the influences of prediction accuracy resulting from different forecasting periods and uncertainty of rainfall input. The results show that:(1) compared with discarding forecasting precipitation in the future, the accuracy of flood prediction has a significant enhancement by considering the forecasting precipitation in a long forecast period while a slight improvements in a short forecast period; (2) the central location of rainfall has a great influence on prediction accuracy, and the allowable error of rainfall center in the upstream is greater than that in the downstream; (3) the greater the forecast rainfall forecast error, the lower the forecast accuracy; (4) the rainfall error has liner influences on the flood volume error and flood peak error, but nonlinear influences on the Nash-Sutcliffe efficiency. In addition, the flood peak time error is mainly affected by the rainfall time error.