Abstract: In order to provide a theoretical basis and scientific guidance for the selection of tree species and effective utilization of water, by using Li-6400 portable photosyntometer, light response of gas exchange parameters of Shepherdia argentea seedlings under different soil moisture conditions was analyzed in Datong experimental base of Qing Hai. The results showed that Pn, Tr and WUE were significantly correlated with PAR and SWC. ①When PAR was 500~2000 μmol/(m2?s) and SWC was 14.35%~21.5%, Shepherdia argentea leaves had high Pn and WUE. ②Compared with other water conditions, Shepherdia argentea had higher photosynthetic capacity and stronger adaptability to light conditions at low PAR under the mild water stress condition. ③Photosynthesis of Shepherdia argentea was higher under the moderate water stress condition than those under other water conditions, so WUE of Shepherdia argentea did not decline but increased. When PAR was 500~2000 μmol/(m2?s) under the severe water stress condition, WUE was still at high level, which indicated that Shepherdia argentea was of high efficiency of water utilization and could adapt to changes of water and other environmental factors through its own physical regulations, so as to keep WUE at high level. It was concluded that Shepherdia argentea had high ability to adapt stress (strong light, drought) and can be widely cultivated in loess plateau region.