Abstract The ability to maintain water balance is crucial for survival of small rodents that live in arid environments. To understand physiological adaptations of Mongolian gerbil (Meriones unguiculatus), Brandt’s vole (Lasiopodomys brandtii), desert hamster (Phodopus roborovskii), Campbell’s hamster (Phodopus campbelli) and striped hamster (Cricetulus barabensis) that live in Inner Mongolia grasslands with different water conditions, we compared their renal morphology, nephron density and urine osmolality. The medulla thicknesses of kidney for the 5 species of rodents change with their distribution area, from typical steppe region, semi-desert to desert regions, and increase with the decrease of water availability. The urine osmolalities are higher for arid rodents. There were no significant differences between the cortical nephron densities for the 5 rodent species and juxtamedullary nephron density showed opposite changes. These results suggest that renal morphology and histology indices can be used to assess mammalian kidney urine concentration ability to a certain extent. Kidney structure is flexible in response to environment variation.