Based on the daily wind data of June, 1979 is calculated by an in-direct method the mean thermal field at 90°E meridional cross-section and then the mean meridional circulation (MMC) driven by hetero-geneous non-adiabatic heating with the diagnostic equation for the MMC.The numerical results are compared with those of rotating dishpan experiments and numerical experiments in general circulation as well as with analytical results of empirical orthogonal function. Both the MMC and the second eigenvector field obtained using the empirical orthogonal analysis from daily meridional circulations in June, 1979over the central Plateau are due to heterogeneous non-adiabatic heating, which shows the significant influence of thermodynamic effect of Qinghai-Tibet Plateau on early summer meridional circulation. Finally,the evolution of the MMC during the seasons of the general circulation transition in the northern hemisphere is made clear.