The aim of this field experiment was to find out the photosynthetic response of reed along the water table gradient in Keriya river watershed using Li-6400 portable photosynthesis system.The results showed that:(1)When water table was 2 m below,reed showed a decreasing light saturation point (LSP) and a increasing light compensation point (LCP),suggesting the reduction of potential in the use of light intensity.Meanwhile the decreases in maximum net photosynthetic rate(A_max),light respiration(LR),CO₂ saturation point (CSP),carboxylation efficiency and apparent quantum efficiency were observed with decreasing water table(P<0.05),while water use efficiency(WUE) tended to increase.(2)Under salt stress,the photosynthetic parameters were all lower than that under water stress with A_max 19.98%,LSP 40.61%,LCP 37% and dark respiration (RD) 74.56% lower,respectively.Reed WUE under salt stress was lower than that under drought stress.(3)Compared with reed at dry land,water logged plant showed decreas in A_max,LSP and LCP with 41.32%,14.56%,55.55% lower,respectively.We also found that atmospheric CO₂ enrichment can improve reed salt tolerance through decrease in plant WUE under salt stress,and the A_max of water logged plant.It can be concluded that in arid area,reed has developed counter mechanisms in response to long-term drought and salt stress.