The relationships of the March precipitation anomalies over South China with the associated circulation and the global sea surface temperature (SST) field are analyzed by using observations of March rainfall over South China, NOAA SST data,Niño3.4 index, and NCEP reanalysis data for the period 1951-2005. The possible causes of the March precipitation anomalies over South China were revealed from the point of view of the atmospheric circulation and SST field. The results show that when March rainfall over South China is above (below) normal, a cyclonic circulation (an anticyclonic) anomaly exists in the middle-low-level of the troposphere over the North Pacific Ocean, and an anticyclonic (a cyclonic) circulation anomaly appears over the western Pacific Ocean and the South China Sea. These circulation anomalies are favorable (unfavorable) to the southeast warm-moist air flow and the abnormal cold air in the east of northern China which form a water vapor convergence over South China, leading to a significant increase (decrease) of precipitation. Further analysis showed that the El Niño-Southern Oscillation (ENSO) and North Indian Ocean and South China Sea SST are important external factors that influence the March precipitation anomalies over South China. The influence of ENSO on the March precipitation anomalies over South China is through the western Pacific subtropical high and low-level wind field anomalies, and the influence of the North Indian Ocean and South China Sea SST on the March precipitation anomalies over South China is affected by the vertical circulation and low-level wind field anomalies, as well as the abnormal western Pacific subtropical high.