In arid ecosystems, high temperatures and low rainfall result in reduced carbon fixation. Non-structural carbohydrates (NSCs) (including soluble sugars and starch) represent the products of plant photosynthesis and are mainly involved in the balance between C acquisition and expenditure in life processes. NSCs also reflect the amount of plant carbohydrates that can be used to resist adverse environmental conditions. The C:N:P stoichiometry of plants is associated with important ecological processes, such as an organism’s ability to adapt to environmental stresses. Leaf N is the basis of chlorophyll formation for direct use in photosynthesis. Plant P is indispensable for the transportation of photosynthetic products. Thus, the C:N:P variations in plants are directly affected by the rate of photosynthesis. Leaf N concentration has been found to be positively correlated with NSC fixation ability, and P has been identified as the key element of plant metabolism. Accordingly, leaf photosynthetic capacity and NSC synthesis are not only affected by leaf N concentration but also closely related to P concentration. Therefore, it is important to study the relationship between NSCs and C:N:P stoichiometry in Zygophyllum xanthoxylon to improve our understanding of its survival and growth strategies to xeric conditions. Samples were collected from three dominant communities of Z. xanthoxylon across Ningxia and Inner Mongolia Provinces in northwestern China that differed in mean annual relative air moisture (Plot 1>Plot 2>Plot 3). Plant and soil samples were collected during the growing season (August) of 2014. Soluble sugars and starch are commonly studied NSCs. Plant samples were divided into leaves, stems, and roots to analyze the concentrations of starch (ST), soluble sugar (SS), C, N, and P. The concentrations of SS, ST, and NSCs in stems and leaves decreased from Plot 1 to Plot 3. N and P concentrations decreased, whereas C:N and C:P ratios increased with increasing xeric conditions in roots, stems, and leaves. N:P ratios in leaves were all below 13, lower than the critical ratio of 14 in all three plots, suggesting that N is the limiting factor for the growth of Z. xanthoxylon in xeric environments. Variations were inconsistent in NSCs and C:N:P stoichiometry among the organs. N and P concentrations in leaves were higher than those in stems and roots, while C:N and C:P ratios in leaves were lower than those in stems and roots in three plots. The correlation of C:N:P stoichiometry with NSCs showed that N concentrations positively correlated with SS concentrations in roots, stems, and leaves, whereas N concentrations in leaves negatively correlated with ST in roots. Stems and roots may act as nutrient sinks, and Z. xanthoxylon may alleviate water deficit-caused N limitation by increasing N and P use efficiency. Z. xanthoxylon adapted to drought by regulating the accumulation and distribution of NSCs among organs. Osmotic potential is regulated by conversions between ST and SS in the root system; more carbohydrates were allocated to roots and stored as ST with enhancing drought stress. N is the key factor in the transformation of ST to SS and ST storage in the root system.