Based on the reanalysis data (1°×1°, 4-times-a-day’s)of NCEP, the high-density automatic gauge’s rainfall data and the conventional meteorological data, a synoptic and dynamic diagnosis of the continuous rainfall event from June 17 to 21,2005 in Jiangxi Province is made. The results show the event was caused by 9 local meso-β scale cloud clusters and 12 eastward-moving and growing strong convective rain clusters. Low level convergence, upper level divergence and up-ward flows are very important to the intensification and maintain of the meso-β scale convective cloud clusters and rain clusters, therefore they are related well to the intensity of the heavy rain. The jet-cores appear, develop and move eastward continuously in the 850hPa southwest jet stream with the meso-scale cloud cluster and convective rain cluster in the 200km north of the jet-cores.