Leaf shapes are not only the useful indicators in plant taxonomy,but also the important factors affecting energy and material exchange in leaves.In this paper,we collected and scanned the leaves of Nitraria tangutorum in Dengkou of Inner Mongolia Autonomous Region(the mean annual precipitation 145 mm) and Minqin of Gansu Province (the mean annual precipitation 115 mm) and N. sphaerocarpa in Dunhuang,and then analyzed leaf shape parameters with Image - Pro Plus6.0 image processing software and leafδ~(13)C values in the isotope laboratory of the Chinese Academy of Forestry.The result showed that:1) as leaf area increased with increasing water availability the increases in the leaf length and width were asynchronously;2) with the same leaf width,the 1 eaves of N.tangutorum and N.sphaerocarpa were significantly longer in high water available conditions;and 3) although there were significantly differences in water availability between Dengkou and Minqin,as well as between the bottom and middle of the alluvial fan near the East Lake in Dunhuang,the leafδ~(13)C values of N.tangutorum or N.sphaerocarpa were similar in different water conditions(P>0.05).Our results suggested that the ratio of leaf perimeter to area would be an important factor which linked leaf shape to plant water physiology.During growing procedure of leaf area,leaf length increase was prior to its width to alleviate the reduction in ratio of perimeter to area and maintain water use efficiency of the plant. Leaf shapes are not only the useful indicators in plant taxonomy, but also the important factors affecting energy and material exchange in leaves. In this paper, we collected and scanned the leaves of Nitraria tangutorum in Dengkou of Inner Mongolia Autonomous Region (the mean annual precipitation 145 mm) and Minqin of Gansu Province (the mean annual precipitation 115 mm) and N. sphaerocarpa in Dunhuang, and then analyzed leaf shape parameters with Image - Pro Plus 6.0 image processing software and leaf δ ~ (13) C values ​​in the isotope laboratory of the Chinese Academy of Forestry.The result showed that: 1) as leaf area increased with increasing water availability the increases in the leaf length and width were asynchronously; 2) with the same leaf width, the 1 eaves of N. tangutorum and N.sphaerocarpa were significantly longer in high water available conditions; and 3) although there were significantly differences in water availability between Dengkou and Minqin, as well as between the bottom and mi ddle of the alluvial fan near the East Lake in Dunhuang, the leaf δ ~ (13) C values ​​of N. tangutorum or N.sphaerocarpa were similar in different water conditions (P> 0.05) .Our results suggested that the ratio of leaf perimeter to area would be an important factor which linked leaf shape to plant water physiology. During growing plant of leaf area, leaf length increase was prior to its width to alleviate the reduction in ratio of perimeter to area and maintain water use efficiency of the plant.