Abstract: In this paper，a simulation experiment has been made to indicate the mountain microclimate effect of Mentougou area based on a three dimensional quasi-static equilibrium air-soil coupling model developed in G-Chen coordinates system ．The study indicates that the mountain air temperature and surface soil temperature are almost opposite change to terrain height and temperature contours tendency is basically in accordance with terrain contours tendency．The temperatore in the lower mountain valley is higher than that in the east plain in winter and the temperature diurnal variation is the most obvious in summer．Surface soil temperature has close relationship with the air temperature and its distribution is similar to that of the air temperature．Relative humidity over mountain surface is increasing along with terain height．Owing to the effects of "X”valley shape overlaying Mentougou area．the lower level wind vector has convergence to mountain cap and brings valley breeze during daytime and is opposite during nighttime．