We selected plant communities in different soil types in enclosures and grazing lands on the desert steppe of China to explore community composition, niche characteristics of populations, utilization of limited resources, and mechanisms of inter-specific competition and co-existence, employing classical niche theory. A total of 42 species, belonging to 36 genera and 15 families, were recorded in 90 quadrats, and Leguminosae, Gramineae, Compositae, and Chenopodiaceae were the dominant families. The biomass and density of vegetation in aeolian sandy soil habitats were the highest, the niche breadth of annual plants was frequently higher, and the importance value of Artemisia scoparia was the largest. The vegetation coverage and the niche breadth of perennial plants was relatively higher than those of the annual plants, and the importance values of Lespedeza potaninii and Stipa capillata in sierozem soil habitats were the maximum. Grazing decreased the number of species and the density of perennial herbs, while annual herbs increased in number of species and density, and there was no significant effect on the density of semi-shrubs. As the dominant species in this area, A. scoparia had the highest niche breadth and total niche breadth in different habitats. The niche overlap index of A. scoparia and other species was higher in the grazing and short-term enclosure habitats, while the proportion of niche overlap index decreased in long-term enclosures, especially in sierozem soil habitats. The degree of niche overlap index among species in the weathering bedrock habitats was the largest, while it was the smallest in the aeolian sandy soil habitats. A. scoparia was mostly distributed in the center of the DCA ordination map, indicating that it played an important role in the community, had a strong competitiveness for limited resources, and showed good adaptability to the environment. The heterogeneity of habitats was the key factor leading to the difference in community composition and niche characteristics. Therefore, the ecological adaptability of species in different soil types should be considered in vegetation restoration and protection measures in the desert steppe to avoid niche function conflict.