Based on the conventional observations and Doppler radar data, a strong convective weather process occurring over Fujian on 4—5 May 2005 is analyzed. The process happened over the prefrontal warm sector. It showed that the release of unstable energy was triggered by the invasion of weak cold air. Strong updrafts produced by the coupled high-and low-level jets were favorable for occurrence of the severe weather. Strong water vapor transport and atmospheric instability contributed to the formation and development of three squall lines, which were the weather systems directly causing the severe weather. The analyses of radar data indicated that three echoes grew into the squall lines in turn after they moved into Fujian Province.