Abstract:Based on daily precipitation data of five weather stations of Dongying City from 1971 to 2004, the characteristic of rainstorm change and the produce reasons in this region are studied by using Petitt method and composite analysis. The resu lts show that the inter decadal variation of Dongying rainstorm has pr esented 3 characteristic time intervals since the 1970s. The abrupt change of ra instorm happens in 1974/1975. The rainstorm has a trend of escalation before abr uption, and it quickly reduced after abruption. 1990 was the second level chang e point, afterward the rainstorm frequency obviously increased. Increase in Dong ying rainstorm after 1990's is attributable to the advantageous upper air circul ation background, frequent interaction between the north cold air and south warm and humid air streams. As a result of the Dongying special geographical positio n, the terrain and landform influence cause the Dongying precipitation's climate characteristics being inconsistent with that of Shandong Province. The former c hange is counter parabola shape, but in the whole province it appears to be consistently decreas ing tendency.