CO2 flux and its impact factors were measured by an eddy correction system in Stipa grassland.There were distinct diurnal and seasonal variations with an inverted U-shape diurnal change in CO2 flux.There was obvious change in July,and the maximum uptake and emission were-0.56 and 0.83 mg/(m2·s),respectively.Latent heat flux,sensible heat flux,net radiation flux and photosynthetic active radiation were related to CO2 flux.There was no obvious correlation between soil temperature and soil water content with C...