Abstract: In order to select salt-tolerant plants for planting in saline soil, 2-year-old Nitraria tangutorum and Tamarix chinensis are used as experimental material. At the same time, NaCl concentration gradient is setted 0 (CK), 100 (Y1), 200 (Y2), 400 (Y3), 600 (Y4) mmol﹒L-1 in order to study photosynthetic diurnal variation of them under salt stress. The results showed that: (1) The trend of the average photosynthetic rate (Pn) of them under salt stress was basically the same with non-salt stress conditions; (2) The photosynthetic ability of Nitraria tangutorum was stronger than tamarisk; (3) With salt concentration increasing, the decline rate of Nitraria tangutorum was greater than Tamarix chinensis in average daily net photosynthetic rate (Pn) and carboxylation efficiency (CE);The water use efficiency (WUE) of Tamarix chinensis under salt stress was higher than non-salt stress, but the WUE of Nitraria tangutorum was higher than the comparison only in Y1 and Y2 processing, and the WUE of Tamarix chinensis was always greater than Nitraria tangutorum. (4) Tamarix chinensis began to appear non-stomatal limitation caused by salt-stress from Y3 treatment, white Nitraria tangutorum appeared from Y1 treatment. In summary, the salt tolerance of Tamarix chinensis is stronger than Nitraria tangutorum and Tamarix chinensis is more suitable for planting under the conditions of the study area.