Abstract: The Black Gobi Desert is widely distributed in northwest China, with a total area of about 2×10⁵ km². The general climate can be characterized as having a high evaporative demand, with variable but low precipitation, making it the most arid of China's dryland areas. Because of this special climate, there are a wealth of natural resources and an ideal place for exploring the relationship of plant species diversity and environmental factors in extreme arid environment. In this study, we sampled 174 plots across the research area to examine the influence of the climate on plant species richness patterns. Different growth forms (shrub and herb) were also analyzed to demonstrate how the richness-climate relationship differed among functional groups. Results showed that climate accounted for 62.3% of variation in total species richness, with 37.7% explained by other undetermined factors. Furthermore, 3.5% and 16.4% of total species variance was explained by energy and moisture factors, respectively, while 42.4% was simultaneously explained by the two factor groups. These results indicated that energy and moisture played key roles in shaping species richness patterns in the study area. However, only 37.9% of variation in shrub species richness was explained by energy and moisture factors, and the water-energy dynamic hypothesis could not explain shrub species richness in arid regions. These results suggest that the response of species richness to climate showed obvious differences among functional groups as well as interspecific interactions, and the ecophysiological characteristics of species had significant influence on community richness patterns.