The northern slope of the Kunlun Mountains is next to the Taklamakan Desert, which is the most arid center of the Asian continent belonging to the Xinjiang-Uighur Autonomous Region, NW China. The main plant types in the desert grassland at an altitude between 2100 and 2600 m are Calligonum roborovskii, Ceratoides latens, Sympegma regelii, and Seriphidium korovinii Poljak which are the very important source of livestock food in winter. The plant over conserves water, prevents wind erosion, and maintains ecological stability. Desertification in this area became a serious problem recently and caused sandstorms, erosion as well as sand deposition. Researches on protection and recovery of the vegetation on the northern slope of the Kunlun Mountains are of great importance. C. roborowasikii, C. latens, S. regelii and S. korovinii, are very important four species on the northern slope of Kunlun Mountain. The gas exchange of these plants is closely related to the ecological conditions. It is an effective way to reveal the mechanism of plant adaptation to environmental conditions. Water potential is the most sensitive degree of water condition in plant. Low water potential indicates good water condition of the plant. Accordingly, high water potential reflects that the plant lies in drought stress. Water use efficiency is an important index to distinguish the ability of the plants adapt to drought environment. It can be divided into instantaneous water use efficiency and long-term water use efficiency. Long-term water use efficiency is difficult to be acquired. Many studies suggested that stable carbon isotopic content and long-term water use efficiency are closely related. The content of carbon isotopes in plant leaves is used as an indicator for long-term water use efficiency. The technology has been widely used in plant physiology ecological research. In this study, gas exchange, water potential characteristics in seasonal courses and δ¹³C values of these plants were studied. The results showed that the gas exchange diurnal courses of C. latens, C. roborowasikii and S. regelii displayed a single peak pattern with double peak pattern of S. korovinii. Within the four species, C. roborowasikii displayed a high P_n, T_r and the highest WUE; While those of S. regelii were low P_n and T_r; C. latens was high P_n and low T_r; S. korovinii displayed a low P_n, high T_r and the lowest WUE. The two decline of C. latens in P_n was due to the low carboxylation capacity of the leaf mesophyll; the effect of G_s contributed to the first deline of C. roborowasikii in 12:00-14:00, while the second decline might be due to the two factors. Different species had different mechanisms to adapt to drought stress. C. roborowasikii and S. korovinii maintained higher water potential to delay dehydration. Comparatively, C. latens and S. regelii maintained lower water potential to endure dehydration. When trying to establish the relationships of WUE and δ¹³C, only some species were found to have a good consistency.