Abstract: In this paper,a steady-state, quasi-geostrophic, 34-level spheircal coordinate model with Rayleigh friction, Newtonian cooling and the horizontal thermal diffusivity is used to investigate the thermal effect of the Qing-hai-Xizang plateau on formation and maintenance of the mean monsooa circulation over South Asia.The computed results show that only topographic effect of the Plateau can not form the South Asian high and the monsoon circulation over South Asia, but the diabatic heating over the Qinghai-Xizang plateau may play an important role for formation and maintenance of the South Asian high and the mean monsoon circulation over South Asia.The computed results also show that the diabatic heating over the Qing haiXizang Plateau play an important role for formation of a strong south west wind belt over the Indian peninsula,extending onto the southern of Japan.