To test the application effects of ROSE2.1 in the short-time forecasting, nowcasting and early warning of disastrous weather and further produce marked effects of dual-polarization radar in monitoring and early warning of severe convective weather in Qiandongnan Prefecture, this paper analyzes a severe convective weather event that occurred in Qiandongnan Prefecture, Guizhou Province, on the night of May 5, 2023 based on the C-band dual-polarization radar data of Rongjiang and the high-level and surface meteorological observation data. Besides, the ROSE2.1 radar products are verified and evaluated as well. The results are as follows: (1) This severe convection process was triggered by the combined influence of upper trough, low vortex shear and surface convergence line. The large CAPE value, strong vertical wind shear, unstable stratification of dry-cold at the top and warm-wet at the bottom, and suitable wet bulb 0° C layer height provided favorable conditions for the growth and maintenance of severe convective storms. (2) The maximum reflectivity of the supercell storm with high VIL values and high echo top heights increased before the hail occurred, and its height first jumped to near or beyond the -10 ℃ layer and then rapidly descended. Clear ZDR columns and KDP voids can be found on the dual-polarization parametric profile. (3) The UAM products of ROSE2.1 have higher warning accuracy for this case, and a 20 km2 alarm setting has the best performance in this case. This suggests that ROSE2.1 has a good indication effect on the severe convective weather in Qiandongnan Prefecture. It can serve as an important reference for forecasting and warning of severe convective weather after the parameter correction is done.