Abstract: Recent studies indicate the inverse phase relation between East Asian and South Asian summer monsoons on the interannual scale. In our paper, NCEP/NCAR data and outputs from GCM transient simulation are analyzed to further appeal that the relation might also exist on the orbital scale and it well links with the Paleo-ENSO evolution. During the El Niño-like conditions, the East Asian summer monsoon is strengthened but the South Asian one is decreased. However, these responses are distinctly inverse when the La Niña-like events occur. The similar responses of monsoon systems on different time scales could provide better explanations for our geological records.