Abstract: Based on daily precipitation observations from 305 national weather stations over South China from 1961 to 2013 and NCEP/CFSR 6-hourly reanalysis data with 1°×1° resolution between May and June from 1980 to 2013, giving the definition of sustained torrential rain and torrential rain days during the pre-flood season in South China, we have analyzed the characteristics and the large scale circulation situation, and induced four typical circulation patterns of sustained torrential rain events. The results indicate that the sustained torrential rain events during the pre-flood season in South China mainly occur between May and June, and show a quasi-periodic oscillation of 20 years. Torrential rain in the first five years of the 1960s mostly appeared in June, from the late 1960s to 1980s much in May, from 1990s to 2013 mainly in June, and that in May clearly increased after 2006. Torrential rain event generally continues 3-4 days, and events lasting for more than 10 days only occurred 4 times. The circulation patterns that cause the sustained torrential rain during the pre-flood season in South China are classified into four types, i.e. East Asian trough bottom pattern, two ridges and one trough pattern, multi-vortex pattern and zonal pattern. Among those patterns, the East Asian trough bottom pattern and the two ridges and one trough pattern occur more frequently than other two patterns, with mainly between late May and late June. Meanwhile, the zonal pattern occur the least, with mainly between early May and early June. Different patterns of sustained torrential rain events present the different circulation characteristics at 500 hPa in the middle high latitudes. They also present general characters, including being propitious to north cold air shift southward to affect South China, West Pacific subtropical high (SH) and south branch trough over the Bay of Bengal in the low latitudes being stable, and southwest warm and wet airflow at 850 hPa dominating in South China. Compared to torrential rain events of continueing 3-5 days, those continueing about 10 days are characterized in circulation pattern by SH stretching towards west and being stronger, short wave trough being more active over South China, and southwest monsoon at 850 hPa stretching towards west and north and its wind speed being stronger.