It is crucial to well forecast severe convective weather like hail and provide better service during summer in Beijing. Synoptic dynamics and mesoscal e characteristics of two severe hailstorms are analyzed by using conventional ob servation and the data from automatic weather stations, Doppler radar and wind p rofiler, etc. Comparisons show that they differ greatly from each other on the c irculation pattern, local weather condition and mesoscale system. The coupled up per and lower jet flows, energy condition and the vertical wind shear, conduced more to the occurrence of the May31 hail event. It was under the direct influe nce of supercell structure. In contrast, the June7 hail event developed from a t ypical squallline. Evolvement of the two hailstorms and areas of hail fall hav e good relations with their mesoscale systems. For the May31 hail , the influen cing system is on mesoγscale, while it is on mesoβscale for the June7 hail on. Warning and forecasting of the former hail event is relatively more difficu lt. To well monitor and nowcast these sudden events, full use of the high spatia l and time resolution detection data is needed in future.