Abstract: Using the MaXPol dual polarization radar observation of 26 hail cloud cells and hail data for inversion,the characteristics of polarization parameters and changes in strong center echo top height before hail were statistically analyzed,and a case study was conducted on the most severe hail disaster process.The results indicated that:（1）The hail index of the radar was Z_h（reflectivity factor）＞50 dBZ,ρHV（correlation coefficient）≤0.8,-2 d B＜Z_dr（differential reflectance）＜1dB,and the top height of the strong center echo should at least exceed the-10 ℃ layer.The duration before hail was 6-12minutes,and the average duration of large hail was 1.6 times.（2）Before the hailstorm,the trend of the top height of the strong center echo in large and small hail was consistent,but the growth rate of the top height of the strong center echo in large hail was significantly greater than that in small hail within4-5 minutes.（3）Only the strong central echo top of the large hail could break through the-30 ℃layer.（4）The case study found that the strong center did not correspond to the hail area one by one.During the generation and development stage,the hail area was concentrated in the correlation coefficient ring behind the strong center,hanging in the 0--20 ℃ layer.In the mature stage,the spread of hail areas included a strong center,and the suspended hail area began to collapse to the ground,leading to the onset of hail.