Stipa breviflora (Stipa breviflora Griseb.) and Cleistogenes songorica (Cleistogenes songorica (Roshev.) Ohwi) are two dominant species in the critically important desert steppe of northern China. Under the interference of grazing, the two species will have the phenomenon of plant cluster fragmentation to varying degrees. Therefore, when the two plant populations appear in the same plant community, what changes will happen in the inter-specific relationship during grazing has important guiding significance for its regulation of plant community and function. To study this, we observed populations of wild S. breviflora and C. songorica in field under a suite of grazing intensities and at a variety of scales. The density changes of dominant species S. breviflora and C. songorica in desert steppe in Inner Mongolia were studied under four grazing intensities (no grazing, CK, 0 sheep·ha-1·half year-1, light grazing, LG, 0.93 sheep·ha-1·half year-1, moderate grazing, MG, 1.82 sheep·ha-1·half year-1, heavy grazing, HG, 2.71 sheep·ha-1·half year-1) and six scales (5 cm×5 cm, 10 cm×10 cm, 20 cm×20 cm, 25 cm×25 cm, 50 cm×50 cm and 100 cm×100 cm). Results showed that grazing changes the relationship between dominant species. With the increase of grazing intensity, the densities of S. breviflora and C. songorica increased, and the increase was more obvious with the increase of scale. Under heavy grazing conditions, the dominant populations of clustered grasses in Inner Mongolia desert steppe resisted the interference of high-intensity grazing by reducing inter-specific competition ability (increasing inter-specific affinity).