An EOF analysis of the decadal variability of sea temperature anomaly fields at upper-ocean standard levels has been performed in this paper,and the abrupt change feature of sea temperature has been tested by use of movable t-test technique.The analysis detects that there was a significant inter-decadal abrupt change of temperature from the surface to different depths in the subsurface layer around 1980.At different depths in the subsurface there existed 4 types of abrupt change modes,their formation was close related to the southwestward subduction route of North Pacific sea temperature anomalies.The decadal signal subduction in the window region of the North Pacific propagated southwestwards to the subtropics, and met the anomaly siginal which propagated northeastwards from the West Pacific at about 160 meters level in the themocline.Therefore,the influence of the former on ENSO decadal variability might be indirect,the latter played a more important role.