Abstract: In this paper, we used the hail storm field experimental data in Gausu Province in 1979—1980 to choose several typical cases based on the different synoptic patterns and to divide into two types. Then the composite diagnostic analysis has been done by the averaged hourly surface mesoscale meteorological fields and the probability of radar echo, shower and hailfall. Two kinds of the processes of different mesoscale systems have been obtained. The diagnostic analysis of the meteorological elements indicated that the divergence, moist static temperature analysis of the meteorological elements indicated that the divergence, moist static temperature advection, and vertical velocity are closely related to the mesoscale systems of hail storm over the northeastern Tibetan Plateau. The areal convergence of hail storm which has a certain prior indication can be used for nowcasting the convective weather