A mini supercell was observed in northwestern Shandong province, China on 27 September 2002. The storm was within 80-km of range from the Jinan radar. The structure and the development process of mesocyclone were detected. At the first hour in the case, the storm appeared as a multicell storm. In the second cell remarkable velocity shear was detected at 4-km level, but it did not reach the mesocyclone criterion. The third cell developed rapidly and soon became a mini supercell with V-notch and BWER. About 40 minutes later mesocyclone characteristics were detected. According to a series of 6-slice products SRM (56), the velocity shear was initially observed at 1-km level and then developed upward. The mesocyclone existed almost 90 minutes with the average diameter of 5 km and it`s vertical range between 3.5 km to 6 km. The rotating velocity was about 17 m/s, and the momentum 170000 m**2/s. At the end of the case the mesocyclone contracted by shrinking the top downward and the base upward. It disappeared at 4.1 km level. During the strongest period of the mesocyclone hails with maximal diameter of 13 mm were reported but no hazard winds occurred, perhaps because the mesocyclone is high above surface and did not touch down. Another cause was due to the low CAPE (352 J/kg) and the supercell was moderate relatively. The precipitation on the path of the storm was 3 mm to 10 mm.