Based on the monthly Standardized Precipitation Evapotranspiration Index(SPEI),ocean temperature data from ORA-S4,and National Center for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR) reanalysis data during 1961-2014,this study investigates the decadal shift of autumn drought in South China and its possible relationship with Heat Content(HC) in the tropical Indian Ocean.Results show that the main spatial distribution of autumn SPEI change in South China is in the same phase,with an obvious interdecadal change from wet to dry around 1988.It is further noted that there exists a significant positive relationship between SPEI in South China and HC in tropical western Indian Ocean in autumn,indicating that autumn drought in South China will be corresponded to a lower HC in tropical western Indian Ocean.The lower HC in the tropical western Indian Ocean plays an important role in the decadal drought in South China in autumn.There is an obvious zonal dipole pattern of HC anomalies shown as "<" type in the tropical Indian Ocean in autumn.The positive HC anomalies in the tropical eastern Indian Ocean,which are possibly affected by the negative HC anomalies in the tropical western Indian Ocean,are closely related to the less OLR,more precipitation and higher sea surface temperature(SST) in the tropical eastern Indian Ocean and western Pacific(TEIWP) region.These changes will give rise to an enhanced East Asian Hadley cell,and then a subsidence motion anomaly over South China,resulting in a decadal drought in this region.In addition,the positive SST anomalies over TEIWP will make the northwestern Pacific subtropical high get larger than usual,and extend westward.It also induces cyclonic circulation anomaly around the northwestern Pacific.In such cases,South China is controlled by northerly wind anomaly,reducing the amount of water vapor transported to South China.As the interdecadal change of SST in TEIWP is an important physical process for the HC anomalies in tropical western Indian Ocean,which influences the decadal shift of autumn drought in South China,a series of numerical experiments using NCAR CAM5.1 verify that the decadal warming of SST in the TEIWP region plays an important role in causing the decadal autumn drought in South China.