Based on the daily precipitation data of 756 stations in China and NCEP/NCAR reanalysis data, the low-frequency variation characteristics of 30-90 d continuous precipitation in eastern China during flood season from 1961 to 2011 and its relationship with atmospheric low-frequency oscillation (LFO) are studied. The results show that the more frequent precipitation pattern is the dominant mode of the low frequency variation of the continuous precipitation in flood season in South China (SC). The negative geopotential height anomaly and cyclonic circulation anomaly in the lower troposphere and the circulation anomaly slightly shifted northward in the upper troposphere provide large-scale situation field for the low-frequency variation of continuous precipitation in flood season in SC. When the ridge line of the western Pacific subtropical high(WPSH) maintains around 22°N, the water vapor transport from the Bay of Bengal and South China Sea maintains the active phase of continuous precipitation in flood season in SC, and the LFO system of the subtropical atmosphere spreading to the northeast has a modulating effect on the continuous precipitation in flood season in SC. In addition, the low frequency variation of precipitation in flood season in SC also has the evolution characteristics of north-south migration.