Based on 11 observation stations precipitation data in Shanghai region from May to September during the period 1979 to 2008, the change characteristics of annual and month and genesis of torrential rains in Shanghai region in recent 30 years were analyzed. The results indicate that torrential rains in Shanghai region have turned to strong, local, extremely short-time change trend since 1995. The torrential rains are mainly concentrated from June to September. They occur frequently in July and August, which are mainly short-time and local ones, and arise commonly in June and September, yet, least in May. There are more persistent torrential rains than short-time ones in June, while on the contrary in September. The analysis of weather systems of torrential rain in Shanghai region shows that torrential rains induced by stationary fronts take place most frequently and occur persistent and strong ones when they are stable, otherwise become short-time and weak ones. Torrential rains brought from warm area systems occur second frequently and the kind weather system is a main synoptic type which leads to the short-time and local torrential rain of Shanghai region in summer. Additionally, torrential rains caused by typhoon, typhoon shear, typhoon inverted trough, depression, cold front, warm front and east wind disturbance have a certain proportion. Torrential rains induced by warm area have increased since 1995, but these of stationary fronts have, mainly due to climate warming and heat-island effect, gradually decreased since 2000.