A meso-β scale severe convective weather occurred in Southwest Guizhou on May 2, 2020. A disastrous gale of 42m/s occurred in Anlong, Qianxiang, and the maximum hail diameter was 25mm in Luohan in Pu''an and the maximum hourly rainfall was 66mm/h at Ceheng station. The conventional ground observation data, high altitude observation data, Doppler weather radar data and NOAA HYSPLIT model synchronous driving data are used to analyze the weather process. The results are as follows: (1) This process is mainly affected by the high altitude trough, the shear line of the middle and low levels, the surface convergence line and the Yunnan thermal low pressure. (2) The atmospheric unstable stratification is obvious. The elevation and condensation height is low and the sounding of Baise presents "hourglass" structure at 20:00. The strong vertical wind shear of 0-6km, high dry warm cover index, obvious dry layer in the middle troposphere and momentum downward transmission in the upper troposphere are conducive to the formation of thunderstorm and gale. The height of wet bulb zero layer and -20℃ layer are conducive to the growth of hail. And the good water vapor condition is conducive to short-term heavy precipitation. The backward trajectory model HYSPLIT simulates four water vapor transport paths of Xingren station: local, West, southwest and northeast; (3) In the process, the satellite infrared image shows that the elliptical hailstorm cloud cluster develops and moves, the TBB center is lower than -60℃, and the convective cloud top extends higher; (4)The three echo paths are northwest southeast; when the hail occurs, the radar echo presents the characteristics of "hook", three body scattering spike, echo hanging, strong divergence at the storm top, vertical liquid water content jump, high echo top and so on; when the short-term heavy rainfall occurs, the echo center is low, the low-level strong radial convergence, and the radar product rain is strong; (5) When the 42m/s disastrous gale occurred in Anlong Qianxiang, the 65 DBZ reflectivity factor core was located at 6 km, the echo gradient was large, and the reflectivity factor core decreased rapidly. There were lateral inflow slot, radial positive and negative velocity pairs, radial convergence in deep and middle layers, strong divergence at the top of the storm, obvious rotation and other characteristics, and the positive velocity ambiguity reached 35m/s. The "narrow tube effect" of topography has an increasing effect on the occurrence of this disastrous gale.