23 cases of large-scale heavyrain storms over Sichuan Basin in 1959-1982 are selected and divided into three types. Resultant analysis are then made respectively for each type according to their middle and low-level tropospheric potential height field and wind field. It is shown that each type of heavyrain storm occurs respectively in different synoptic characteristic environment.These conclusions canbe applied to forecast the large-scale heavyrain storm over Sichuan Basin.