By way of a low-order spectral model,the two-layzer quasi-geostrophic model is translated into an eighthorder set of nonlinear ordinary differential equations in which the thermal forcing and dissipative effect are incorporated. Within a certain range of the parameter θ_C^*,which approximately describes the S-N thermal forcing between the subtropical continent and the ocean to the south,an equilibrium of the flow pattern is exhibited. When the θ_C^* value exceeds the critical point,a periodical zonal oscillation of the subtropical high cells can be stimulated showing various oscillational forms.