Abstract: In this paper, by using multi–spectral analysis, some factors such as the southern oscillation index, sea surface temperature and trade wind index have been calculated, and the coupling oscillation between the southern oscillation and the sea surface temperature over the equatorial Pacific is revealed. It is found that their variations are seemed to be out of phase, and there is a few months phase difference between the sea surface temperature and the southern oscillation. In addition, the correlation between southern oscillation and the trade wind over the Pacific is analysed.