Abstract: From diabatic quasi-geostrophic equations of motion, the characteristics of diabatic Rossby waves under the thermal effects of the Tibetan Plateau are analyzed. When the basic zonal flow is barotropic, it is demonstrated that the cooling of the Tibetan Plateau in winter not only facilitates the meridional propagation of Rossby waves, but also is an important driving mechanism of the intraseasonal oscillations in the middle and high latitudes. The large-scale heating of the Tibetan Plateau in summer prevents Rossby waves from propagating meridionally. When the basin zonal flow is baroclinic, it is found that the cooling of the Tibetan Plateau in winter facilitates the instability of Rossby waves, while there is a threshold in the influence of the heating of the Tibetan Plateau in summer on the stability of Rossby waves.