Abstract:The large scale features of the Mei Yu front assoc iated with heavy rainfall along the Pearl River valley in South China, the Yangt ze River valley and the Huai River valley in 2007 are discussed. During the peri od 1 16 June, the Mei Yu front extended along Pearl River valley with intense rainfall. In th e middle of June with the first westward extension of the subtropical anticyclone in the West Pacific, the Mei Yu front jumped to the Yangtze River where it las ted for nine days. With the second westward extension of the subtropical anticycl one in the end of June, the Mei Yu front jumped to the Huai River valley, where it lasted for two weeks and brought about severe floods with great damages. The dynamical and thermodynamic characteristics of the Mei Yufront in the three valleys are compared. It is found that the dynamical and the rmodynamic structures are all the same and we suggest to use the same “Mei Yu front” for the three valleys. 　During middle of July there was a disastrous flood in the Huai river valley. The mechanism of the torrential rainf all that brings about the severe flood is discussed in the second part. It is fo und that with the intense develo pment of ridge and trough system along the subtropical jet stream in North China , there was an intense development of a deep trough along 110°E, which induced th e development cyclone genesis and front genesis in the Mei Yu frontal zone fr om 1000 400hPa. With the development of the cyclone genesis and front genesi s along the Mei Yu front, there was rapid upward motion along the front zone ca using intense rainfall along the Mei Yu front.