Abstract: The Xihu desert wetland，Dunhuang，Gansu Province，China is quite important and peculiar in China or even in the world. However，until now，little research has been focused on the microclimate and CO2 flux characteristic in this area. This paper reports the characteristics of daily variations of microclimate and CO2 flux in the Dunhuang Xihu desert wetland by analyzing the data observed in the Xihu desert wetland of Dunhuang for summer and winter continuous fine weather in 2012. Results indicated a level of turbulent mixing in agreement with the observations in Xihu region for summer and winter weather，justifying their reliability，and there existed updraft prevails in this reg- ion in the two seasons. The temperature and humidity of topsoil were both sensitive to the air temperature and solar heating in summer and winter，but the variation amplitude in winter was less than that in summer. The components of the ground surface radiation in the Xihu desert wetland of Dunhuang in summer and winter both showed typical daily variation，but it was lower in winter，and the ground upward longwave radiation and atmospheric longwave radiation were higher than that in other high altitudes. The maximum value of carbon absorption both appeared at about 11 o’clock every day in the two seasons. The concentration of carbon dioxide both gradually decreasedas time went on，therefore，the desert wetland ecosystem was a carbon sink during the observation period in summer and winter，but it was weaker as a carbon sink in winter.

Key words: surface layer, microclimate, energy budget, CO₂ flux, contrastive analysis, Dunhuang, extreme arid region