An analysis is made of the process of a hail-storm event occurred in Shandong Province on 27 September 2002. The primary results indicate that the main influencing systems include the southward movement of an upper-level cold trough in cooperation with the low-level shear line and the frontal zone on the ground. The cold advection in the upper air and the warm advection in the lower level resulted in the large-scale unstable zone of potential energy from the middle-level to the low-level of the troposphere. The coupling of a meso-scale low pressure and the divergence zone of an upper-level jet caused strong upward motion. This is a typical small super-cell storm. The mesocyclone is found in the storm by analyzing the radar echo.