Based on NCEP/NCAR monthly reanalysis data from 1948 to 2012,the interdecadal variation of summer water vapor transport over eastern China is investigated using the 9-yr moving average,EOF analysis and compositive analysis methods.Results show that summer(June—August) water vapor transport is characterized with a turning point from strong to weak around 1975.The abnormal area of water vapor transport mainly locates in the eastern China.Water vapor transport from South China Sea to eastern China has interdecadal variation in June.Water vapor transport from the Bay of Bengal,South China Sea and western Pacific in July(Indian Ocean,South China Sea and western Pacific in August) to eastern China also has interdecadal variation.Distribution of summer water vapor transport flux vectors is consistent with that of the first component of interdecadal water vapor transport before and after the interdecadal variation.Significant water vapor flux convergence zone locates in the southwest to the northeast China.In the northern Yangtze River,water vapor convergences(divergence) are caused by the wind field convergence(divergence) and the water vapor advection,but in the southern Yangtze River,which is mainly caused by the wind field convergence(divergence).