Abstract: After determination of the physiological property of photosynthesis and water relation of seven species of Saxoul forests including their intensity of photosynthesis and respiration, chlorophyll conent, stoma status, distribution of photosynthetical outcome, primary productivity and utilization efficiency of water, etc. It was discovered that Eremophyte species have high efficiency of photosynthesis and water utilization. The average intensity of photosynthesis of Haloxylon ammodendron during June to September is 8.02 CO2·mg/g dry weight. Hour, close to the Populus bolleana (8.39) which is amesophytes. The transpiration coefficient of Haloxylon persicum (250.12mg water/g dry weight) is about the half of Populus bolleana (502.45). The high efficiency of photosynthesis and water utilization of Eremophyte may be attributed to long adaptation to the ecological environment of high temprature and aridity. Currently, Saxoul forests are only used as firewood by local residents, which is neither economical nor rationable and needs improvement.