The first heavy rain process during 2002 flood season of Hunan,with strong rainfall intensity and wide scope,occurred on 12—14,May 2002. Analyzing synthetically the process from several aspects,such as the general circulation,the physical factors,the satellite images,the radar echo,the numerical weather forecast products,etc.,it is shown that the key forecasting the heavy rain process succeeding and serving well is making best use of the above-mentioned products besides understanding the weather pattern deeply.