Water-use efficiency (WUE) and the stoichiometry of plant-soil carbon (C), nitrogen (N), and phosphorus (P) are key indicators of plant growth, while stand quality is an important index for evaluating afforestation. Yet it remains unclear how WUE and stoichiometric characteristics respond to changes in stand quality in desert ecosystems. To that end, we studied the community characteristics of sand-fixing Caragana korshinskii stands differing in age (planted 10, 30, 50, and 70 years ago) in Mu Us Sandy Land, China, and measured their leaf water use efficiency (WUE) and leaf-soil C:N:P stoichiometry. The relations among the stand quality index, leaf WUE, and plant-soil stoichiometry were analyzed. After 70 years, WUE was at its lowest level, but only significantly lower than that of a 10-year-old C. korshinskii stand. Afforestation years had differential effects on C, N, and P nutrients and their stoichiometric characteristics in leaves and soil. For soil, its total P barely increased. Irrespective of stand age, the N:P ratio of leaves was > 16, which suggests P is the main factor limiting the development of C. korshinskii plantations. Notably, WUE decreased significantly as the stand quality index increased while soil stoichiometry responded more strongly than plant stoichiometry. These results can guide investigations into the role of C. korshinskii stands in plant and soil recovery effects, providing a scientific basis to evaluate the rational use of C. korshinskii sand-fixing forest in afforestation.