Based on the routine data and the observations of CINRAD/SA radar and automat-ic weather stations,a squall line affecting Fujian on May 22,2005 is analyzed.The squall line is a kind of instable and strong convective weather caused by the air with upper-layer dry and lower-layer wet in front of the upper-troposphere trough.The Mesoscale structure,such as bow echo,strong rear inflow and weak echo region on the inflow entrance etc,with the squall line,caused the disasterous wind.