Abstract: By using regular meteorological data,physical quantity fields,satellite imagery and Doppler radar echo data,we analyze the mesoscale features and the conditions of 4 successive heavy precipitation processes in Yunnan caused by storms over the Bay of Bengal in the early Summer.The results show that the life of the storm over the Bay of Bengal is 2 or 3 days and the cloud-top temperature of the storm is always below –65 ℃.Storms over the Bay of Bengal affect Yunnan by mesoscale convective cloud clusters,peripheral cloud bands or weaken themselves as they are moving to the Northeast.The Tibetan shear lines and vortexes,NE-SW convergence channels and southwest wind convergence supply favorable circulation background and dynamical conditions.There are many common features in Dopplar radar echoes.They are usually about 35～45 dBZ strong and move to the east and produce successive precipitation in Yunnan and the mesoscale features of southwest jet and wind rotating clockwise with altitude not only are favorable for storms over the Bay of Bengal to transport warm and humid air current over to the north,but also are favorable to convection development.