The Black Gobi Desert covers a large area in the northwest of China, with a total area of about 200,000 km². The general climate of the Black Gobi can be characterized as having a high evaporative demand, with variable but low precipitation, making it the most arid region of the country's dryland areas. Nevertheless, despite being considered the most dry and bare ecosystem in the world, it is affluent in natural resources. Because of its harsh environment and poor accessibility, systematic studies of plant diversity in the Black Gobi Desert are lacking. Understanding the underlying causes of geographic plant diversity gradients in arid and semiarid regions is important for the conservation and sustainable use of biodiversity there. However, the underlying mechanisms behind the Black Gobi Desert's plant diversity patterns are still elusive. Therefore, the aim of our study was to analyze the plant community composition, as well as the species diversity of the Black Gobi ecosystem. We sampled 174 plots across the Black Gobi to demonstrate the vegetation pattern and its relationship with the environmental factors. We observed a trend of the plant communities becoming poorer and simpler in composition while vegetation cover decreases. Moreover, the overall structure and composition of the plant communities were simple, the majority of plants having an importance value lower than 0.1. The plant communities consisted mainly of Haloxylon ammodendron, Reaumuria songarica, Nitraria tangutorum, and 10 other species. Species diversity showed non-significant latitudinal and longitudinal trends, but was significantly influenced by climate, elevation, and topography. In addition, structural factors were most important in determining the spatial variation of species diversity. The result of a detrended cross-correlations analysis (DCCA) indicated that climate, elevation, topography, soil texture, and surface cover had a significant effect on community composition and plant distribution. Overall, the vegetation spanned a gradient in elevation,soil texture and water availability. Plant species are limited by water availability, and it should be noted that plant community composition was strongly related to changes in elevation, which influence soil texture and water availability. In sum, the spatial heterogeneity of the soil texture and water availability were the main factors to determine plant distribution and species diversity.