Abstract: The photosynthesis characteristic and the water potential of four plants:Tamarix ramosissma, Haloxylon ammodendron, Calligonum caput-medusae and Elaeagnus angustifolia were studied in the same environment at the desert-oasis ecotone of Moyu county in the south fringe of Takelamkan Desert in August of 2010, we analysed and compared the physiology characteristics of the four plants. 1) Among the four plants, light response curves are basically the same trend, showed that photosynthetic rate (A) rapidly increases with the photosynthetic active radiation (PAR) increases, when the PAR reached light saturation point, appear decline trends;as C₄ plants, C. caput-medusae and H. ammodendron have higher light saturation point (LSP) and light compensation point (LCP), which embodies the advantage of the high photosynthesis of C₄ plants; however, other parameters of photosynthesis, such as A_max, and R_day, are not in complete accord; 2) H. ammodendron has a lower early morning and midday water potential, indicating that H. ammodendron rely mainly on water recovery capability at night to cope with drought environment;dawn water potential had a highly significantly except C. caput-medusae and E. angustifolia (P<0.01), midday water potential also had a highly significantly except T. ramosissima and E. angustifolia (P<0.01); 3) Changes of proline and soluble sugar are similar, the content in C. caput-medusae is higher than the other three plants(P<0.05);The E. angustifolia has the highest content of MDA, while the content in C. caput-medusae and H. ammodendron are lowest; the content of MDA is differed significantly except H. ammodendron and C. caput-medusae (P<0.05); 4) Based on the analysis in the relevant membership function using the average of four plants for drought resistance in this order, the results show that: the four plants in the order of drought resistance is H. ammodendron>T. ramosissima>E. angustifolia>C. caput-medusae.