The boundary layer height(BLH)is an important parameter to characterize the atmospheric boundary layer. In this research, the characteristics of profiles of potential temperature and radio-sounding balloon ascent rate inDunhuang in August 2009 were analyzedusing nine radio-sounding data. The results show that the ascent rate of radio-sounding balloonand vertical velocity of balloon can be used to determine the BLH. By analyzing the BLH determined from profiles of potential temperatureand ascent rate, the biggest BLHexceeds over 4 300 m in Dunhuang in summer of 2009 and the mean BLHis about 3 500 m. The BLH in the cloudy day is lower than that in the sunny day. The BLH beforenoon is lower than that of after noon. The theoretical basis why ascent rate of radio-sounding balloon can be used to determine BLH was introduced in this paper. This study diversified the methods of determining BLH.