Abstract: A three-dimensional hailstorm numerical model is used to simulate and analyze a hailstorm in Xichang on 29 April 2013.The simulated results show that the cases of Hailstorm had an accumulation zone of supercooled raindrops.Graupel is the main hail embryo, and hails grow mainly through the process of hail hitting the freezing cloud water, followed by hitting freezing graupels.Solid and liquid precipitation accounted for 48% and 52% of the total precipitation, respectively.However, hail accounted for 94% of solid precipitation.Based on the analysis of the microphysical processes involving cloud ice, snow, graupel and frozen drops, it can be seen that during different stages of the development of hail clouds, hail formation mechanism is different.