Based on meteorological observation data, Doppler weather radar observation data and ERA5 hourly reanalysis data, the heavy hail weathers in Tongwei County of Gansu Province on May 30 and 31, 2020 were analyzed. The results are as follows: (1) The hail process on May 30 was a dry hail process, while the process on May 31 was a mixed strong convection with wet hail process. (2) Both two processes occurred during developing and moving eastward of the same low-trough, and the difference of influence system at 700 hPa led to difference of water vapor and energy conditions in middle and low levels, which was the main reason for occurrence of dry and wet hail. (3) The diagnostic analysis of physical quantities showed that the energy on May 31 was higher, the water vapor condition was better, and the static instability and convective instability were stronger than those on May 30, so the hail diameter was larger and precipitation intensity was stronger. (4) On the radar PPI image of reflectivity，the meso-scale characteristics of the two processes were obviously different, which was very helpful for classification and identification of severe convective nearly warning.