Abstract: From the night of March 30 to the early morning of March 31, 2021, a severe convective weather event occurred in northern Jiangxi, accompanied by widespread short-duration heavy rainfall and large-sized hail. This region is located in the spring convectively active zone of the middle and lower reaches of the Yangtze River, where severe convection tends to be sudden and difficult to identify. Based on ERA5 reanalysis data, Tianqing minute-level ground rainfall observations, and Nanchang S-band dual-polarization weather radar data, this study analyzes the synoptic background, radar echo structure, the relationship between dual-polarization parameters and surface precipitation, as well as microphysical characteristics of the event. The results indicate that the event was a typical elevated convective process. The strong echo region exhibited a distinct ZDR arc, a high KDP area, and an inflow notch, reflecting strong updrafts and a mixed-phase particle structure within the storm. The hail-producing region showed typical ZDR and KDP columns, while the non-hail precipitation region displayed a good match of high ZDR and KDP values below the 0 ℃ level. Time series analysis at the minute scale revealed that the peaks of ZDR and KDP on average preceded the precipitation peak by 8.8 minutes and 6 minutes, respectively, indicating good early warning potential. The ρHV was more sensitive to particle phase and exhibited relatively low stability. The polarimetric signature of the three-body scatter spike (TBSS) was characterized by negative ZDR, a KDP hole, and a sharp radial decrease of ρHV. These findings provide a valuable reference for the identification and nowcasting of severe convection in Jiangxi and similar regions.