In order to study the evolution characteristics of the Z_DR column in an isolated cell, the hailing process of an isolated cell on May 8, 2018, is analyzed by using X-band dual-polarization radar data combined with ground observation data and reanalysis data. The results show that: (1) In the development stage of an isolated cell, the Z_DR column increased rapidly. After the jump, the number of SWAs (Supercooled Water Areas) and HDGs (High Density Graupels) above the 0 ℃ layer increased sharply, and the change rates were 26.7 bins per minute and 11.8 bins per minute, respectively. In the mature stage, the depth of the Z_DR column extended to the nearly -20 ℃ layer, the microphysical reaction in the monomer intensified, the number of hail increased rapidly, and the generation rate was 105.8 bin/min. The Z_DR column was transformed into a Z_DR hole (Z_DR<1) with an area of 210 bins, which indicates the ground hail location. (2) Hail occurred after the collapse of the Z_DR column. The height of the Z_DR column dropped below -10 ℃ due to the dragging effect of solid precipitation. When the small hail fell below the layer of 0 ℃, it melted and formed a water film on the surface, resulting in the Z_DR large value area near the ground during the hail fall. (3) The interaction between the microphysical process and thermal dynamic in the isolated cell promoted the formation and development of the Z_DR column. In this paper, the evolution characteristics of the Z_DR column in different stages of an isolated hail storm are analyzed, and the corresponding hail storm model is established, which is of great significance to the early warning and prevention of local hails.