In the face of global climatic changes, exploring how plant adaptation and responses to drought vary among different regions is crucial to understand and predict its geographic distribution. In this study, to explore the drought adaptation and responses of the dominant species in the semi-arid Eurasian Steppes and their differences among the species distribution regions in terms of growth, physiology and RNA-seq transcriptome, Stipa krylovii was chosen as the study object and a seed source (3 regions: eastern, middle and western regions) × soil moisture treatment (3 treatments: control, light drought and heavy drought) two-factor experiment was conducted. (1) Four growth traits for individuals from the western region were significantly lower than those from the other two regions. By Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analysis on gene expressions of individuals from each treatment, unique enriched pathways were found mainly under heavy drought. (2) The decrease in the number of tillers with the increasing drought was much lower for individuals from the western region than those from the other two regions. By KEGG functional enrichment analysis on differentially expressed genes (DEGs) between heavy drought treatment vs control, enrichment pathways of individuals from the eastern and middle regions mainly regulated energy metabolism and metabolism of other amino acids; and those from the western region regulated biosynthesis of other secondary metabolites and carbohydrate metabolism. (3) Clustering analysis based on gene expressions separated the western region from the other two regions under the same soil moisture treatment. This study indicates that drought adaptation and response mechanisms of S. krylovii vary among different regions, especially between individuals from the western region and the other two regions. These findings are essential for us to understand the adaptive evolution of population and germplasm resource protection for this important species in semi-arid grasslands.