With the observation data, FY-2 cloud images data and the NCEP reanal yzed data, the development characteristics of an explosive cyclone which occurre d during June 22-23, 2003 is analyzed by synoptic diagnosis and numerical simula tion with MM5. It is indicated that the explosive cyclone was caused by combinat ion of the eastward moving high level trough over the great band of Yellow River and the warm wind sheer over southern Shandong Province. The explosive cyclone over the land during summer occurs in the place where the cyclonic curve of heig ht field meets the exit port of the jet, and it develops abruptly when it pass f rom the right to the left of jet. The development of explosive cyclone needs hig h level jet, and the southwest low level jet and southeast low level jet provide it strong warm advection and vapor transport. The explosive cycloneurs in the high energy fields, following the strong development of the ascending movement with strong divergence on high level and strong convergence on low lev el. The air has strong convective instability.