Firstly, this paper iVustrates the global structure of the sea surface temperature (SST) anomalies associated with El Nino and El Niño events and the Southern Oscillation (SO) structure associated with the sea level pressure (SLP) anomaly.Secondly the typical structure of the SO forced by global ocean heat source and real topography was simulated by using of IAP two-level atmospheric general circulation model.The simulated location of the SLP anomaly centers over the eastern Pacific differs significantly with the observations if only the SST heat source without topography was considered.It suggests that the SO may be a response to the global SST anomaly under the real topography.