Abstract: Based on the data of hail shooting from 1961 to 2000 in Bayannor and the data of the 713 radar from 2004 to 2008,the characteristic of the spatial and temporal distribution of the hail shooting was analyzed by the methods of mathematic statistics and chart analysis. The different grades of annual hail shooting were defined by the gradual cluster. The results showed that the hail shooting was during the period of April to September,mainly concentrated from the second ten days of June to the last ten days of August,which took 68.6% of the total hail shooting days. There was a linear correlation between annual hail shooting days and disaster days caused by the hail shooting. The hail shooting's frequency in 1960s and 1990s was lower than that in 1980s. The years from the end of 1970s to the mid of 1980s were severe hail disaster years at the first grade. The years of the late 1990s were mid-severe hail disaster years at the second grade,or light-severe hail disaster years at the third grade. The research results provided the references for the hail disaster forecast and prevention.

Key words: Bayannor, Bayannor, Locomotive route of hail cloud, Climatic characteristics of hail, Grades of hail shooting disaster, Gradual cluster