By using the grid dataset of wind field at 850hPa(24,48 and 72hour) of ECMWF model and real time dataset of objective wind field, the forecast capability of 850hPa wind and the weather systems of ECMWF model is tested for the 13 rainstorms processes causing the flood of Changjiang River basin from June to August of 1998. Results are in favor of understanding the numerical weather forecast products and correcting real time forecast operation, and improving the forecast ability for rainstorms as well.