Abstract: By using twice a day grid data of ECMWF and the TBB data of Japan GMS,together with the daily precipitation data over stations in South China during June and July,1994,situations of two successive heavy rain processes in South China、activity of summer monsoon(mainly the South China Sea monsoon)and the possible relationships between them are analyzed in t his paper.We have found that the summer monsoon in 1994 is active,summer monsoon(especially the South China Seasummer monsoon)as well as the low value area of TBB,is related closely with the heavy rain processes with low frequency oscilation mode(with 30～60 day period).Heavy rain process always corresponds to a strong impulse or strong of monsoon.Strong monsoon flows bring moisture to South China and the major moisture source comes from South China Sea.Although the two heavy rain processes occurred under diff erent conditions,both of them took place in the maximum moisture converg ence and convective unstable regions.