Using various data such as conventional observation data, radar and satellite data, reanalysis data from EC and realtime global sea surface temperature data from NCEP, the environmental conditions of a hail event on 3 March 2018 in Hainan are compared and examined and the its mesoscale features are analyzed. The results show that largescale circulations were depicted with a midlevel drycold WSW jet, lowlevel warm SW flows and the surface southwest trough from 2 to 4 March. On 3 March, the regional atmospheric stratification was in a transition from stable to unstable. The local increased unstable energy was strongly released by the trigger of seabreeze front. The favorable 0to6 km vertical wind shear, 0 ℃ and 20 ℃ heights are conducive to the development of the hailstorm. On 2 March, the regional stratification near the Hainan Island was stable and the CAPE value was low; on 4 March, the Hainan Island was at the entrance of the lowlevel gale core with divergent water vapor, and the vertical circulation of the seabreeze front was restrained. Those were unfavorable for the development of severe convections. This hailstorm had some typical radar characteristics. After the hailstorm moving into the static cone areas of Doppler radar, the downtoward propagation of highlevel jet pulse and the increase of the vertical wind shear of 0 to 5 km and 0 to 3 km can be detected by utilizing the wind profile radar, which is of great significance to the judgment of the evolution of the storm cell. The convective cell initially appeared at the junction of the surface convergent line and the dew point front in the central Danzhou, and developed into a hailstorm in the overlapping areas of the northside of the sea breeze front and the dew point front in the north of Haikou to Danzhou. New cells developed around the dew point front at the front of the hailstorm.