This paper primarily discusses the synoptic and climatic characters in heavy rain during Meiyu flood period (June-July) based on the thirty year (1981-2010) observational data at 46 stations and the reanalysis dataset from 1981 to 2010. Main circulation characters and impacting systems of heavy rain in Jiang Huai Basin at 500 hPa and wind distribution characters at 850 hPa are summarized by integratively analyzing abundant historical examples. A conceptual model of heavy rain and study respects of medium range forecast are put forward. Ten durative heavy rain weather processes in the last thirty years are discussed, and the results show that the easterly propagation of Rossby wave is in favor of occurrence of the durative heavy rain weather processes in Jiang Huai Basin. The downstream development of Rossby wave provides some new ideas for medium range forecast.