[Objective] The contents of C, N, P, and their ecological stoichiometry characteristic contained in foliage, branches, litter, and soil of different age grades of Populus alba L. var pyramidalis stands were determined in order to provide a theoretical basis for the sustainable development of farmland shelterbelts in the Alar Reclamation Area, South of Xinjiang Wei Autonomous Region.[Results] The contents of C, N, P, and stoichiometric characteristics were:① C content followed the order of litter (395.14 g/kg)>foliage (365.29 g/kg)>branch (363.84 g/kg)>soil (9.47 g/kg); N content followed the order of foliage (13.37 g/kg)>litter (9.10 g/kg)>branch (7.31 g/kg)>soil (0.72 g/kg); P content followed the order of foliage (0.46 g/kg)>branch (0.43 g/kg)>soil (0.37 g/kg)>litter (0.27 g/kg). ② Compared with the national average value, foliage-branch-litter-soil showed a pattern of low C, low N, low P. The total C content showed a trend of "increasing-decreasing-increasing" with the age grades. The total content of N in the four age-grades showed a trend of decreasing with increasing soil depth except for the third age grades. The total contents of P generally increased with increasing age grades, and were significant between different age grades in the same soil layer (p<0.05). ③ The soil C:N ratio (13.05) was higher than C:N (11.9) in China. The C:P and N:P ratios (24.04, 1.83) were lower than those of soil C:P and N:P ratios (60.0, 5.20) in China. ④ Soil N and P contents in the 0-80 cm soil layer of Populus alba L. var pyramidalis were significantly negatively correlated with foliar N content (p<0.01), and positively correlated with foliar P content (p<0.01). Litter N content was significantly positively correlated with surface soil N content (p<0.01). There was a significant negative correlation between litter P content and 20-40 cm soil P content (p<0.01).[Conclusion] N and P contents are the limiting factors for the growth of Populus alba L. var pyramidalis shelterbelts because of lack of management and protection in the Alar Reclamation Area. Therefore, N and P must be added appropriately by artificial measures so as to improve soil fertility and the quality of farmland shelterbelt stands.