The satellite cloud picture,radar echo,the intensive observation and the conventional data were used to analyse a strong mesoscale convective weather process which happened between the northern Yellow Sea and Shandong Peninsula on the first day of July in 1996. The results show that the unstable energy,which was caused by the low temperature trough in the upper air and the ascending of temperature in low level and on the ground,is the formation condition of the strong convective system. Those factors,such as mesoscale convergence zone,meso cyclone,uneven heating near the surface and the convergence of land and sea breeze,prompt the development of the convective system. An important condition of the system developing is that the extraordinary energy is produced when the convective cloud clusters merge and enhance. The quasistatic state of the cloud cluster is the main reason for the rainstorm and the continued hailfall.