Abstract: The European Centre for Medium-Range Weather Forecasts has released seasonal GloFAS Seasonal runoff and SEAS5 precipitation ensemble forecast products in recent years. The runoff forecast of six control stations and the areal precipitation forecast of four sub-areas in the upper Yangtze River are selected. The prediction ability of the two products for dry scenario in the upper Yangtze River reservoirs impounding period are evaluated by calculating and analyzing the indicators such as AUC, ROCSS and reliability. The evaluation results show that the two products could predict the occurrence of dry scenario one month in advance, and the products tend to over-predict the possibility of dry scenario events, which needs to be considered in practice. This study can provide a scientific basis and technical support for reservoir impounding operation based on medium and long-term forecast in the upper Yangtze River basin.