The SF100 Heat pulse sensors based on the heat compensation theory were applied to study the diurnal and seasonal changes of trunk sap flows for Caragana korshinskii. The soil moisture content at 0～300 cm layer was measured with a tube-type time domain reflectometry (Tube-TDR). The solar radiation, the maximum and minimum air temperature, relative humidity, wind speed, wind direction and precipitation etc. were also measured with an automatic weather station where the reference crop evapotranspiration was provided simultaneously. The diurnal and seasonal variations of sap fluxes, the flow velocity at different positions in the trunk and the sap fluxes under different weather conditions were analyzed. The correlation between the sap flux and the meteorological factors was also analyzed by SPSS 11.0 statistical software. Results showed that the trunk sap flow varied regularly in the diurnal term and the sap flow velocity decreased with the inserted depth into the sapwood. Magnitude of sap flow changed considerably between sunny and rainy days. The order of the main meteorological factors affecting the sap flux of Caragana korshinskii trees were: vapor pressure deficit>solar radiation>air temperature>wind speed.