By means of the numerical prediction data， wind profile and Doppler radar data， and automatic meteorological observation data from the main landing site， an analysis is made of a hail storms process on 14 September 2008.The results indicate that during the hailstorm， the essential meteorological factors changed fiercely， and the cold front of the invasive Mongolia low along with a mesoscale convergence line， moving close to the main landing site， triggered the rapid development of strong convection； in the earlier period vertical wind shear increased obviously； the main formation causes include deep wet convective instability stratification， intense vorticity advection， and vertical ascent movement.TBB decreased rapidly in the earlier period， and the nonecho dome area on the RHI chart is the hail source area.The hailstorm occurred on the north side of the axis of 〖WTBX〗θ〖WTBZ〗se tongue and the south side of the upper front zone.