Based on the daily precipitation data of 74 observational stations in South China and the daily NCAR/NCEP reanalysis dataset in 1957—2001,the features of different precipitation periods in the pre-flood season(AMJ) in South China are compared.The main results are obtained as follow:the pre-flood season in South China is composed of the frontal precipitation period and the summer monsoon precipitation period.The former mainly appears in April,accompanied with a typical transition circulation pattern from winter to summer,where in strong subtropical westerly jet streams prevail in the high level over South China,the atmospheric stratification is stable,and the moisture is mainly originated from the westerly transport over the Arabian Sea and the easterly transport on the south side of WPSH;before the onset of SCSSM,the subtropical high dominates over the SCS and the moisture in South China mainly comes from the westerlies over the Arabian Sea,the easterlies on the south side of WPSH and the southwesterlies over the Bay of Bengal.After the onset of SCSSM,the subtropical high withdraws out of the SCS,accompanied with the strengthening of the cross-equatorial moisture transport from the Southern Hemisphere;the summer monsoon precipitation peaks in June when the South Asian High prevails over the Tibetan Plateau and South China,vigarous convection develops and the powerful cross-equatorial flow cross the Bay of Bengal and transports moisture towards South China.