Stem sap flows of 18-year-old Caragana korshinskii and 8-year-old Artemisia ordosica plants were monitored continuously with Dynamax stem flow recorder for a growing season in 2008 under nature conditions in a revegetated desert area. Environmental factors such as solar radiation, air temperature, relative humidity, wind speed, and precipitation were measured meanwhile with eddy correlation system. Diurnal and seasonal variations of sap flow rates and their correlation with meteorological factors and reference evapotraanspiration were analyzed. Results show that the curves of stem sap flow rates in the whole growing season are obviously single-peak. Stem sap flow of Caragana korshinskii usually starts at 06:00 and increases gradually, reaches peak point at about 12:00, then gradually decreases, and sap flow exists at night. Stem sap flow of Artemisia ordosica usually starts at 08:00 and increases gradually, reaches peak point at about 14:00—16:00, then gradually decreases, but there is no sap flow at night. There is a significantly linear relationship between sap flow rate and reference evapotranspiration. Sap flow rate is also significantly correlated with environmental factors, and the order of the main meteorological factors affecting the sap flow rate of Caragana korshinskii is solar radiation>relative humidity>air temperature>vapour pressure deficit>wind speed, the order of the main meteorological factors affecting the sap flow rate of Artemisia ordosica is solar radiation>vapour pressure deficit>relative humidity>air temperature>wind speed.