Abstract:The inter decadal variation of summer monsoon rainfall in East Asia and its rel ationship with Pacific Decadal Oscillation (PDO) are investigated by using month ly precipitation reconstruction over global land, the monthly sea surface temper ature anomaly (SSTA) of Hadley Center for Climate Prediction and Research, and t he National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset. It is revealed that both the inter de cadal mode of the summer monsoon rainfall in East Asia and PDO occurred ap parent inter decadal shift around 1976. Moreover, there exists close relation b etween summer monsoon rainfall and PDO on inter decadal time scale. PDO can gen erate anomalous atmospheric circulation in the low level troposphere, which is homologous with the inter decadal variability of summer monsoon circulation in East Asia. It suggests that the external forcing of PDO in lower troposphere pos sibly exerts influences on the inter decadal variability of the East Asia summe r monsoon circulation, and finally leads to the inter decadal variability of th e summer monsoon rainfall in East Asia.