Bryum argenteum is a globally widespread species adapted to extreme arid environments. In this study, the external morphology and anatomical structure of 17 populations of B. argenteum from Xinjiang were examined. The external morphology and internal structure of this plant species in semi-arid, arid, and extreme arid environments have been compared to explore its adaptability. The results showed that there were notable differences (P<0.05) in plant height, leaf length and width, awn tip length, plant cross-sectional diameter and leaf cell length and width among the populations of B. argenteum. As the intensity of the aridity increased, the plant height decreased, the awning of the leaf elongated and the leaf area shrank. The coefficient of variation in the leaf area was larger in population C than in populations B and A. The coefficients of variation for leaf area (0.3478), height (0.2957), and the awn length (0.2349) were found to decrease, which further indicated that the leaf of B. argenteum were the most sensitive to changes in the external environment. Together, this suggests that the external morphology and anatomy of B. argenteum have strong plasticity, which may be an important survival strategy for the moss to adapt to the arid environment. Our results provide a theoretical basis for rational utilization and conservation of wild plant resources and ecological vegetation restoration in arid regions.