On the basis of 1950—1999 fifty year data of Hadley Center global SST,NCEP/NCAR reanalysis and China 160 station precipitations,investigation has been conducted on the relationship between summer as well as autumn Indian Ocean Dipole(IOD) and autumn precipitation over China.Evidence shows that the IOD,both in summer and autumn,bears a close positive correlation with autumn rainfall over southern China.Further analysis shows that during the occurrence of positive IOD episode it is the southwestly(cyclonic) anomalies in the middle(lower) troposphere over southwest China that cause the plenty water vapour and then the increase of rainfall in that region.