The decadal change in the summer monsoon system over the east Asian and western North Pacific is prominent since 1979 and predominantly associated with the sea surface temperature (SST) distribution of equatorial central and eastern Pacific. The monsoon system in the 1979-1993 period is mainly linked to the warming of SST in the NINO3 region (150°W-90°W, 5°S-5°N),which is associated with a combination of developing and decaying ENSO phase. On the other hand, that in the period 1994-2006 is associated to the SST warming in the NINO4 region (160°E-150°W, 5°S-5°N) during the developing ENSO phase. In other words, a decadal change in the principal patterns of rainfall variability over the east Asia and WNP region is associated with the shift of decadal-scale changes in tropical Pacific SST variability. These features are obvious in both observations and model results.