Abstract: A preliminary review is conducted on the mesoscale processes of heavy rain, mainly including: (1) the organizational features and classification of heavy-rain-producing convective system, the structure and formation mechanism of different convective systems, especially the cause of new convective cell regeneration and strati form precipitation formation; (2) the initiation, organization and maintenance mechanism of heavy-rain-producing convective system; (3) the effects of the topography on the initiation and development of heavy-rain-producing convective system and its precipitation efficiency, the related internal physical principles, the limitation of topographical linear theory and the nonlinearity and complexity of topographical effects; (4) the diurnal features, regional differences and its different formation mechanisms of heavy-rain-producing convective system. Lastly, the main scientific issues needed to be further investigated are discussed.