The FLOW32-1K wrapped heat balance sap flow meter was used to conduct long-term continuous observation on the sap flow velocity of Hedysarum leave in the Mu Us Sand land. In addition, the meteorological factors including air temperature (T), solar radiation (R), relative humidity (RH), vapor pressure deficit (VPD), and the characteristics of H. leave sap flow were investigated. The correlations between environmental factors and different temporal scales were determined. The findings revealed the following:(1) the average daily sap flow rates of different diameter classes (3-4 mm, 4-6 mm, and >6 mm) were 5.61 g/h, 9.29 g/h, and 35.30 g/h, respectively. The average daily sap flow was (134.72±82.48) g/d, (223.06±152.20) g/d, and (847.23±403.38) g/d, respectively. Under different weather conditions, the sap flow rate was higher in sunny days than that in rain days, and the change of sap flow rate was higher in day and lower in night, with different months being August > July > September. (2) Solar radiation was the main meteorological factor affecting plant sap flow in different days. At the hourly scale, solar radiation, temperature, relative humidity and saturated vapor pressure could explain more than 75% of sap flow, whiel at the daily scale, the meteorological factors could explain more than 80.8% of sap flow. With the increase of time scale, the number of meteorological factors entering the regression equation decreased, but the explanatory degree to the change of sap flow of H. leave increased. In this study, the change of H. leave sap flow was estimated by meteorological factors and prediction model under the condition that continuous observation could not be carried out in the future, so as to guide vegetation restoration and water resource management in Mu us Sandy land.