Abstract: Considering the processes of non-adiabatic heatinb in the atmosphere and the feedback mechanism of the atmosphere to the ocean, a zonally averaged model of ocean-atmospheric coupled system is constructed. The frequency-analysis of this system shows that there exist long-range (longer than one month) oscillations. The duration of oscillations depends upon the depth of mixing layer in the ocean, the latitudinal location and the intensity of various physical processes, such as convective condensation heating, radiative cooling, evaporation from the sea surface, upwelling of oceanic water by wind stress and regulation of radiation balance by clouds.Based on above the results, the formation and features of ITCXZ are discussed.The computed width and latitudinal location of the covergence zone have been found in fair agreement with the observed facts.