Abstract: Reaumuria soongorica, a drought-tolerant shrub typical of Tamaricaceae, is one of the dominant species in desert areas of northwest China. It functions as a key biotic barrier against desertification due to its strong sand fixation ability and is therefore critical for maintaining the stability of desert ecosystems. The Gansu Corridor (in west Gansu province), is the main distribution range of R. soongorica in China and is characterized by environmental harshness associated with long-term aridity, rare precipitation, high evaporation, extremely high temperatures in summer and freezing conditions in winter. As a consequence, variations in plant morphological traits in this area are primarily accounted for by abiotic factors. Variations in four phenotypic traits of seed including thousand-kernel weight (TKW), seed length, seed width, seed length/seed width in 10 natural populations of R. soongorica in the Gansu Corridor, China, were examined using variance (ANOVA), correlation analysis and cluster analysis to reveal the pattern of variability in seed phenotype. The four phenotypic traits of R. soongorica seeds differed significantly between populations (P<0.01), but showed no significant difference within populations. The average coefficient of variance (CV) between populations across the four traits was 0.019 3, ranging from 0.001 8 for seed length to 0.068 5 for TKW. The average coefficient of variance for each population was the highest for Zhangye1 (0.048 4) and the lowest for Jiuquan2 (0.006 6). The main source of variation was in groups, which accounted for more than 68% of the total variance. All traits were spatially correlated with longitude, latitude, and altitude. Cluster analysis (using Euclidean distances) for all four seed traits revealed that the 10 sampled populations can be grouped into four clusters. The understanding of the seed phenotypic traits of R. soongorica in different populations and the spatial variation in the Gansu Corridor will be fundamental for future research projects on the collection, conservation, genetic evaluation, and utilization of its germplasm. The results can help to design artificial supplementary regeneration and enhance population genetic diversity.