The transpiration water consumption of Haloxylon ammodendron is an important physiological index, which is greatly influenced by many environmental factors. We accurately measured the transpiration water consumption of the individual trees by investigating their sap-flow characteristics in response to various environmental factors. We predicted the transpiration of a single tree with the help of the environmental indicators by building a sap-flow model and environmental factors. Combined with the automatic weather stations, a thermal dissipation probe (TDP) was used to continuously measure the sap-flow dynamics and environmental factors of H. ammodendron in the southern marginal zone of the Gurbantunggut Desert, China. The response of sap-flow velocity to the environmental factors was analyzed, and a relationship was established between the stem sap flow and environmental factors during the growing season of H. ammodendron. The results showed that: (1) the change of sap-flow velocity mainly presented a single-peak curve, or occasionally, a double-peak curve in summer. The amplitudes of daily variation and sap-flow peak were relatively greater in summer than in spring and autumn, and presented a significant difference with the sap-flow velocity during different seasons. In summer, the initial and peak sap-flows were observed earlier in the day, but a weak sap-flow was observed at night. (2) In the growingseason, the net radiation, air temperature, and saturated vapor pressure deficit were the key factors leading to the instantaneous changes in sap flow. The instantaneous sap-flow of H. ammodendron was positively correlated with wind speed, net radiation, saturated vapor pressure deficit, and air temperature, and negatively correlated with actual water vapor pressure and air humidity. (3) The key factors affecting the seasonal change in sap-flow velocity included net radiation, saturated vapor pressure deficit, and air temperature. The daily average flow rate was positively correlated with net radiation, air temperature, saturated vapor pressure deficit, actual water vapor pressure, soil water content, and soil temperature, and negatively correlated with air humidity. (4) The daily transpiration first showed an increasing trend, and then decreased during the whole growing season. In early May, the daily transpiration was 0.21 mm/d, and in the middle of June, it showed a peak-value, which lasted for forty days. The daily transpiration began to decline in late July until it reached a value of 0.10 mm/d. In H.ammodendron study samples, the daily transpiration was 0.35 mm/d and the total transpiration during the entire study period was 53.35 mm, suggesting strong ecological adaptability of H. ammodendron to drought conditions. In the study area, where the ecological environment was harsh because of high temperature and little rain, the water consumption of H. ammodendron was very low, making it the first choice to be used as the ecological restoration and reconstruction shrub in an arid land.