Relation between pre-flood season precipitation anomalies in South China and water vapor transport is analyzed by using the daily precipitation data of 57 stations in South China and the NCEP/NCAR reanalysis daily data for water vapor transport from 1958 to 2000,and the differences between drought and flood years are studied.Results show that anomalous meridional water vapor transport in South China will cause anomalous droughts or floods in South China,but anomalous zonal water vapor transport only causes the local precipitation anomaly;the anomalous water vapor transport in drought and flood years is not a simple out-of-phase relation;and the water vapor coming from the Indian Ocean and the West Pacific do not obviously affect the pre-flood season precipitation anomaly in South China,in fact,the South China Sea(particularly its north)is the key area of water vapor source for the precipitation anomaly of the South China.