Based on the Xingyi Doppler weather radar data, routine upperair and surface observations, a detailed analysis of the atmospheric environmental conditions and radar echo structure of a strong hailstorm which occurred in Anlong, Xingyi and Xingren of the Southwest Prefecture of Guizhou on 14 April 2009 is made, and also the echo structure of the mesoanticyclone that embedded in the left moving supercell is analyzed in detail. The backgrounds for occurrence of the hail storm are intense heatingup of the surface, which leads to the development of thermal depression in the lower atmosphere, the developing eastward mesoα scale trough in the midlevel, and an upperlevel jet stream above the convective location. The eastward convective clouds triggered by the mesoα scale trough evolve into supercells under the influence of the unstable stratification and significant vertical wind shear. The strong hailstorm splitted into a right moving supercell and a left moving supercell at 18:36 BT 14 April 2009, the left moving supercell developed into a strong one, accompanied by a mesoanticyclone with a diameter of 3 km, rotational speed once reaching 30 m·s-1 in average, and travelling leftward along the mean wind (northwest wind) towards the southeast direction, it is a rare but very strong anticyclone supercell; this supercell produced hails up to 40 mm in size. The right moving supercell is accompanied with a weak mesocyclone producing hails of 20 mm in size. The radar echoes displayed the characteristics of supercell: the strong reflectivity echo gradient in low levels, weak echo region and bounded weak echo region, front inflow and rear inflow, hookshaped echo, strong mesoanticyclone and weak mesocyclone, all these lasted for 3 to 4 hours. This article also gives an analysis on the structure of the mesoanticyclone in the strongest stage of hailstorm, and a discussion of the application of VIL (vertically integrated liquid) value in the forecast of hailstorm.