In this research, the variations of foliar stable carbon isotope composition (δ¹³C) and water use efficiency in P.euphratica in different plots are studied. It is found that the values of foliar stable carbon isotope composition (δ¹³C) of P.euphratica in the five plots vary from (-25.80～±0.05)‰ to (-29.19～±0.05)‰, with a mean of (-27.70～±0.13)‰. The average δ¹³C value is the highest in the dune plot, followed by that in gobi plot, with a lowest in riparian plot. The difference in δ¹³C value among different plots is caused by discrepancy in soil water content and groundwater depth. There are two trends of foliar δ¹³C values during the whole growing season. Water use efficiency in P. euphratica in the five plots during the growing season varies from (60.41±0.47) to (95.46±0.47)μmolCO₂·mmolH₂O^-1, with a mean of (75.69±1.37)μmolCO₂·mmolH₂O^-1. The range and average of water use efficiency indicate that P. euphratica is a species with higher water use efficiency. From riparian lowland, sandpile, Gobi plot to Dune plot, with reduction of soil water content and lowering of groundwater depth, the water use efficiency is improved gradually.