Abstract: By using the sounding data from 11 to 18 August 2008 collected in the air－land interaction experiment in Northwest China (NWC－ALIEX), the authors have analyzed the vertical atmospheric structure and boundary layer height in the summer clear days over Dunhuang, China. The results show that the height of the tropopause is at about 15000 m above the ground. It should be the second (subtropical) tropopause. The zero-temperature level varies between 3000 m and 4000 m above the ground. The vapor exists mainly in the lower troposphere below 6500 m above the ground. There is an inverse humidity layer around the zero-temperature level. The westerly and the northwest wind predominate the higher troposphere above 5000 m above the ground. The maximum wind speed of 25－50 m/s occurred between 9000 m and 13000 m above the ground. The thicker atmospheric boundary layers exist in late summer in Dunhuang. The height of the convection boundary layer can reach about 4200 m and the height of the stable boundary layer can be 1300 m.