Abstract: The temporal and spatial distribution characteristics of all hailstones, circulation patterns and physical quantities of large hailstones with hail diameters greater than or equal to 5 mm were analyzed in the Aba prefecture from 2008 to 2017.The hail weather in Aba prefecture mainly occurred from March to October, with the most hail days in May. The daily change characteristics of the hail is mainly concentrated at the 14: 00 p.m. to19: 00 p.m.. According to the spatial distribution, the hailstorms are mainly concentrated in the northwestern region above 3, 000 m sea level. The hail weather conditions in Aba Prefecture can be divided into three typical types: high pressure type in Tibet, northwest airflow type, and high altitude shear type.Under large environments, the middle and low layer shear convergence and stratification are unstable and the cold air on the ground may affect the situation. Hail and other strong convection weather. From the environmental parameters, the 75. 8% of the cases reached the unstable state of dry and wet. More than 75% of heavy hail occurs at 400 ~ 600 hPa vertical temperature difference is above 17℃, 500 hPa ascending motion, BLI is negative unstable atmosphere in the knot, and the corresponding vertical wind shear at 400 ~ 600 hPa exceeds 8. 2 m·s^-1. Most CAPE values in heavy hail days are above 325 J·kg^-1, and CIN values are mostly below 14. 4 J·kg^-1. Most of the SSI values are greater than 226. 4.