Abstract: Photosynthesis and transpiration of main constructive plants (Artemisia ordosica, Caragana intermedia and Salix matsudana) in Mu US Desert were measured with model LI 6000 photosynthesis system in different periods. In addition, the photosynthesis active radiation, relative humidity, leaf temperature, air temperature, intercellular CO2 concentration, stomatal resistance, leaf water potential, soil moisture and so on were also measured. The results showed that photosynthesis and transpiration for different species at different periods were different and closely related to environmental conditions and plant internal factors. Photosynthesis active radiation was the dominant factor, and leaf stomatal resistance also played an important role in plant photosynthesis and transpiration. Different plant species had different responses to natural conditions, among them, Caragana intermedia was more sensitive than the other two species. The effect of soil moisture condition on leaf water potential of Artemisia ordosica was most noticeable. Water use efficiency of Caragana intermedia was also higher as compared with the other two species.