Based on the monthly rainfall data at 160 stations of China,the NCEP/NCAR reanalysis dataset,and NOAA sea surface temperature dataset during 1981-2013,this paper investigates the spatial and temporal distributions of interdecadal precipitation anomaly and its possible causes during the first rainy season in South China.Results show that:(1) Precipitation during the first rainy season in South China has an significant interdecadal turning from negative to positive anomalies,which occurs around 1992,and the center of the most evident anomaly locates in northeast Guangxi and north Guangdong.(2)The significant interdecadal changes in 1990s when South-cold-North-warm in the upper troposphere (40°N bounded) and Lower-warm-Upper-cold in the troposphere occur,make the high-low level circulation field presenting a favorable situation,which is favor of the cold air from the north meeting with the warm and wet water vapor from Bay of Bengal and western Pacific and makes a rising situation of convergence in South China.The 500 hPa meridional circulation at mid-latitude enhances,the Bay of Bengal trough deepens in tropics,the East Asia-Pacific(EAP) pattern shows "+-+" anomalies from south to north,the western Pacific subtropical high is strong and southward,the 850 hPa wind field has an abnormal anticyclone(abnormal cyclone) circulation east to the Philippines(from Hetao of China to Japan Sea),South China is controlled by a cyclone circulation,and the subtropical westerly jet at the upper troposphere is weak and southward.These all result in a significant interdecadal turning of precipitation from less to more during the first rainy season in South China.During the two periods before and after the interdecadal turning,there are significant differences in the strength and position of the Bay of Bengal trough over the tropical,the western Pacific subtropical high and the ridge near the Gulf of Alaska in EAP teleconnection wave train,and the ridge to the south and the west of Lake Baikal over the mid latitude,so the interdecadal anomalies of these systems are the important reasons leading to the precipitation anomaly during the first rainy season in South China.(3)The interdecadal anomaly of sea surface temperature in the key region of South Pacific has great effects on the general atmospheric circulation in East Asia and precipitation in South China during the first rainy season.Sea surface temperature in the key area of South Pacific shows remarkable warming trend in the early 1990s.During the warm(cold) period,South China is controlled by the anomalous low altitude cyclone(anticyclone) circulation,and the upper-tropospheric westerly jet is weak and southward(strong and northward),which makes the abundant(lack) of precipitation in South China.