Abstract: According to the analysis of the GMS digital stretched cloud image and conventional precipitation data, it shows that storm and heavy rainfall in the Changjiang-Huaihe River valley during Mei–yu period of 1991 is mainly produced by mesoscale cloud clusters. They are: vortex-warm front shear cloud clusters and cold front shear cloud clusters. Most of them are meso-β scale cloud clustets. The mean life time is 5—6 hours and the mean minium cloud top temperature is –69℃. It is seen that the vortex-warm front shear cloud clusters are created on the eastern side of the vortex center and in the left front of low level jet axis, while the cold front cloud clusters are located in the confluence site of the rear of Mei–yu front cloud system with the southwest monsoon. In addition, the relationship between cloud cluster top temperature and precipitation are estimated. It is found that the top temperature of 75% of cloud cluster with rainfall of 5mm/h and over is –64℃ or down.