Agropyron mongolicum is the dominant species in desert steppe in Ningxia, China. With strong drought resistance, cold endurance, and wind and sand tolerance characteristics, A. mongolicum plays important roles in soil and water conservation, agricultural production, and ecological restoration. The spatial distribution pattern and association of plant population not only reflect the ecological regulation ability and environmental plasticity mechanism of a population, but also the external manifestation of their status and viability in the community. To clarify the spatial distribution pattern and association of A. mongolicum at different developmental stages, a desert steppe dominated by A. mongolicum in Yanchi, Ningxia was selected as the research object. The spatial coordinates and diameter of individual clusters of A. mongolicum were measured with a 10 m×10 m sample plot. Five cluster degrees consisting of Ⅰ degree cluster (0-5 cm), Ⅱ degree cluster (5.1-10 cm), Ⅲ degree cluster (10.1-15 cm), Ⅳ degree cluster (15.1-20 cm), and Ⅴ degree cluster (>20 cm) were classified according to the individual cluster diameter. Based on the data from the sample plot, the spatial distribution pattern and association of A. mongolicum among different degree clusters were analyzed by adopting the method of point pattern analysis and O-ring function statistic. The results showed that the proportion of Ⅰ and Ⅱ degree clusters was significantly higher than that of Ⅳ and Ⅴ degree clusters in A. mongolicum population, accounting for 79.24% of the total population. The population had adequate regenerative seedlings and exhibited good development trend. The Ⅰ, Ⅱ, and Ⅲ degree clusters mainly aggregated in a small spatial scale, and the aggregation degree strengthened with the decrease in individuals. As the scale increased, the aggregation degree decreased and gradually transformed to random and uniform distribution. The Ⅳ and Ⅴ degree clusters of A. mongolicum appeared as random distribution at all scales. The association between Ⅰ and Ⅱ degree clusters, Ⅰ and Ⅲ degree clusters, and Ⅱ and Ⅲ degree clusters of A. mongolicum showed significant positive relationship at a small scale, and tended to be unassociated with increase in scale. The remaining cluster levels showed no association at the 0-5 m scale.