Based on conventional data,AMS(Automatic Meteorological Station)(data) and Doppler radar echo data,a squall happened in the central southern Fujian Province on 22 March 2005 is analyzed.The results show that Fujian was located in an unstable stratification being the dry and cold at the upper level and wet and warm at the lower troposphere;the approaching of the south trough in the westerlies and the cold front triggered the release of unstable energy.The heavy squall appeared in the superposed zone of the left divergence area around the exit of the upper-troposphere jet and the frontal convergence area of the surface front.The squall's evolution process can be well demonstrated by Doppler radar and AMS data.