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The conventional and intensive observing radiosonde data from the Beijing South Suburb station and NCEP data are used to analyze 30 cases of hails which happened form 2000 to 2009 in Beijing. The results show that the circulation patterns for hail weather can be classified into three weather types: Northeast cold vortex, Mongolia vortex, and trough; the three types of weather patterns occured 12, 10, and 8 times, respectively; hails often happened from 14:00 to 18:00 It can be seen from the characteristics of the large scale weather circulation that there was a dynamic convergence system at each level from 925 hPa to 500 hPa during hail weather. There were deeply dynamic systems passing through Beijing at upper levels. The stream fields of the Mongolia vortex and trough patterns have the typical characteristics that there is a big north west wind velocity area at 500 hPa between Beijing and Inner Mongolia with speed being 20 m/s or above, and a big south wind velocity area at 700 hPa and 850 hPa with the speed being about 12 m/s in the southeast of Beijing. The humidity condition is not very important to hails because the dew point deficit at each level was larger than 5 ℃. The stability parameters are as follow: the temperature difference between 500 hPa and 850 hPa being 28 to 35 ℃, large wind shear at lower levels, DCAPE greater than 800 J〖DK〗·kg-1, LI (Lifted Index) less than 0, DCI (Deep Convective Initiation) between 20 and 30, TT (Total Totals index) between 40 to 50 ℃, the 0 ℃ environmental temperature height between 3000 to 4000 meters, -20 ℃ environmental temperature height being between 6000 and 7500 meters.