EOF,wavelet analysis,composite analysis and t-test are used to investigate the SST of 1950-1998(588 months),and describe spatial and temporal characters of the SST.It is found that there is an apparent transition during middle and later 1970s:eastern and middle Equatorial Pacific SST turns higher,and mid-latitude Pacific SST turns lower,even more distinctly in west wind drift zone.It is also found that the duration of El Nino(La Nina) is longer with greater intensity after(before) 1976 than before(after) the time,La Nina zone has positive(negative) SSTA in the early stage;the course of SST has an ENSO cycle of 2～6 years with annual oscillation of 8～9 years,a interdecadal variation scale of about 22 years and a signal for long term change,the turn being in 1981.