Using Ningbo S-band dual-polarization radar data, NCEP reanalysis data, conventional observation data, and field hail survey data, the weather background and evolution characteristics of dual-polarization radar echo of a severe hailstorm disaster process in the central-northern of Zhejiang Province on 21 March 2020 is analyzed. The results show that: (1) The circulation situation of this hailstorm process which lasted about 4 hours, belonged to the type of low-level warm advection forcing. Hailstorms A and B first moved in the form of strong convective cells and strengthened into supercells, respectively, when moving from west to east. (2) At the typical hailing stages, there existed the obvious three-body scattering spike (TBSS). The extension height of the strong echo (>50 dBz) on the vertical profile exceeded -20 ℃, while the weak echo of the low layer and the hanging echo of the middle-high layer were obvious. On the vertical profile of radial velocity, the lower layer of the hailstorm converged, and the divergent layer was superimposed on it, which made the hailstorm blocks continue to form and grow. (3) The Z_DR hail signal appeared in the hail area, and the corresponding Z_H was greater than 65 dBz, Z_DR was between -2.0 and 0 dB, and C_C was between 0.80 and 0.98. When combined Z_H, Z_DR and C_C to comprehensively judge that there were hail particles in the cloud, and C_C<0.9, the “hole” area of K_DP could also be used as one of the basis for judging heavy hails. (4) HCL products better reflected the distribution and evolution of hails in the air. According to the hail colour scale at low elevation, combined with the height of the zero-degree layer and the value of temperature decline rate under hail clouds, the falling area and size of a hail could be better judged.