The temporal-spatial distribution characteristics of summer water vapor transport over Tropical Indian Ocean (TIO) and its impact on precipitation over South Asia were investigated using monthly datasets of NCEP/NCAR,CMAP precipitation,and NOAA SST datasets.The first leading mode (EOF1) shows that anomalous water vapor transports from South China Sea to the Bay of Bengal,then separates into two branches.Anomalous water vapor in one branch transports westward to Indian Peninsula and the Arabian Sea,and weakens the westerly water vapor transport in the southern tip of the Indian Peninsula and the Indochina Peninsula,resulting in the decrease of precipitation in these regions.The second leading mode (EOF2) shows anomalous anticyclonic water vapor transport from tropical eastern Indian Ocean across western Indian Ocean,Arabian Sea,Indian Peninsula,and Indochina Peninsula.The southern part of the Bay of Bengal and India were controlled by anticyclonic anomalous water vapor transportation with anomalous water vapor divergence,which leads to less precipitation.Meanwhile,the cyclonic water varpor transport over northeast India leads to anomalous water vapor convergence.As a result,more precipitation occurred in northeast India.Furthermore,possible causes for these two modes were discussed.The EOF1 is closely associated with SST warming in the whole tropical Indian Ocean,and the EOF2 is linked with the tropical Indian Ocean Dipole (IOD).