Using the NCEP reanalysis data and observed rainfall data in China from 1951 to 2008, the interdecadal variation in Southern Hemisphere (SH) circulation and the influence of Antarctic Oscillation (AAO) on summer rainfall in eastern China under the various decadal backgrounds was analyzed. The results indicate that interdecadal variation of SH circulation occurred during the late 1970s. While the subtropical highs in the southeastern Pacific and the southern Atlantic were weakened, the Mascarene high, also known as the Indian Ocean subtropical high, was intensified. In addition, the circumpolar low-pressure belt was deepened. The AAO with a negative phase was changed into a positive phase. The influence of AAO on summer rainfall in China was also changed. A stronger AAO in the boreal spring before 1976 related to more rainfall in the southern Yangtze River and in North China and less rainfall in the Yangtze-Huaihe River valley. Conversely, rainfall amounts were higher from south China to the Yangtze-Huaihe River valley and lower in northern and northeastern China after 1976. Therefore, the influence of AAO on summer rainfall in China is related to the decadal background. After 1976, the influence of AAO tended to intensify and extend more northward. When the effects of sea surface temperature are minimal, AAO can be used as an important tool for summer rainfall prediction in China.