Based on conventional data, AMS (Automatic Meteorological Station) data, NCEP reanalysis data of 1°×1° with a 6 h interval, and radar echo data, a squall line weather event on 11 June 2007 is analyzed comprehensively. The weather background, radar echoes, meteorological element fields are diagnosed. The results show that the squall line occurred under an unstable stratification, in which it was dry and cold at the upper level, wet and warm at the lower troposphere; its triggering mechanisms include the uppertroposphere jet, ground shear, vertical wind shear, and dry air intrusion in the middle troposphere; its energy sources include the weak ABL water vapor transportation and energy accumulation.