Abstract: To explore the localized application value of the X-band dual-polarization Doppler weather radar in monitoring and early warning of severe convective weather in Sandu Shuizu Autonomous County ( hereinafter referred to as Sandu County) , this study focuses on the severe hailstorm event in Sandu County on April 16 , 2024 and systematically clarifies the formation mechanism and radar echo characteristics of the event by using conventional meteorological observation data , ERA5 reanalysis data and data from the local X-band dual-polarization Doppler weather radar. The results are as follows : ( 1 ) The severe hailstorm occurred under the synergistic circulation of the pre-500 hPa upper trough , 700 hPa southwest jet , 850 hPa shear line , and surface convergence line . Thermodynamic and dynamic diagnosis shows that in the stage of severe convection development , the strong whole-layer ascending motion and the " low-level convergence with upper-level divergence " configuration provided essential conditions for sustaining convection . Then , during the hailstorm stage , the strong vertical wind shear maintained the tilted storm structure , extending the lasting time of the hailstorm. (2) The radar echo presented typical features of super cells , with hook echo , inflow notch and deep meso-cyclone being the key radar indicators for the severe hailstorm. (3 ) The core polarization parameters for large-size hail diagnosis are as follows: composite reflectivity (CR) > 50 dBz reaching the ground , differential reflectivity factor (Z DR ) ≈0 dB , correlation coefficient (CC) < 0 . 8 , and specific differential phase factor (KDP ) ranging from 0 . 15 to 1 . 1 °/km. The evolution of ZDR and CC at different heights can reflect the microphysical growth of hail particles . In other words , the emergence of a low- level Z DR column , the descent of the Z DR column height , and the horizontal expansion of the CC < 0 . 8 area can serve as precursory signals for hailstorms . These research findings can be used as a scientific basis for the localized application of the X-band radar in Sandu County.