Soil restrictions and water scarcity pose a major threat to agriculture to the extent that they lead to serious reduction in crop yield and food production. Therefore, it is critical to identify crops with an acceptable yield under low-input conditions, which are also tolerant to water shortage and could maintain good soil quality. Recently, a great deal of effort is being devoted to the management of rhizosphere , in order to maximize crop yield in intensive cultivation systems. Hence, this study was carried out in two parts (in drought stress and non-stressed/control conditions) in order to investigate the effect of cultivated and wild barley species on structural stability and quality indicators of the rhizosphere soil. In the first part (without drought stress), 41 barley genotypes from three groups of cultivated ( Vulgare ), Spontaneum and wild genotypes of Hordeum species, and in the second part (in drought stress condition), 10 barley genotypes ( Vulgare and Spontaneum groups) were studied. The results of first part indicated that water repellency and organic carbon content of the rhizosphere soil substantially varied among the barley genotypes, and due apparently to root exudates their values were greater in the rhizosphere of all genotypes compared to bulk soil. The rhizosphere organic carbon content was in the order of Vulgare Spontaneum Hordeum . Consequently, dispersible clay in the rhizosphere was lower than the bulk soil and its value (as an index of soil structural instability) was in the order of Vulgare Spontaneum Hordeum . Results of high energy moisture characteristic (HEMC) showed that about 34 percent of the barley genotypes improved the structure of rhizosphere soil, compared to the bulk soil. Grouping the genotypes based on the principal components analysis (PCA) indicated that five genotypes (mostly from Hordeum group) increased soil water repellency and structural stability (i.e., stability ratio, SR, and volume of drainable pores ratio, VDPR). Moreover, eight genotypes (mostly from Vulgare and Spontaneum groups) increased the soil water repellency and stability index due to an increment in organic carbon content. The results of cluster analysis showed that all the genotypes were categorized in three clusters in terms of their effects on soil structure: First cluster including 19 genotypes and also bulk soil was defined as the weakest cluster due to the least values of SR and VDPR; Second cluster comprising 11 genotypes with the highest values of SR, VDPR, water repellency and organic carbon content, was named as the best cluster in terms of the rhizosphere soil structural stability and quality. The remaining 11 genotypes were included in the third cluster which was intermediate in terms of soil structural stability and quality, though it was found to be closer to the second cluster. The results of second part showed that drought stress had different effects on the root exudates of barley genotypes and consequently on the physical conditions of the rhizospheric soil. In drought stress condition, the rhizospheric organic carbon in three Spontaneum and two Vulgare genotypes, the rhizospheric water repellency in two Spontaneum and one Vulgare genotypes, and the rhizospheric structural stability in four Vulgare and three Spontaneum genotypes were greater than those in non-stressed condition. With the drought stress, the rhizospheric dispersible clay in a majority of barley genotypes decreased. Overall, those genotypes with poor quality of rhizospheric soil in the non-stressed condition, improved the rhizospheric soil quality under drought stress condition. In addition, the increment in structural stability of rhizospheric soil under drought stress (relative to non-stressed condition) for Spontaneum genotypes was greater than for Vulgare genotypes. Considering the marginal soils characteristic to arid and semi-arid regions in iran, adopting barley genotypes capable of improving soil quality attributes along with producing an acceptable grain yield must be taken into account in future studies. Keywords: oil structural stability, Root.exudates, Drought stress, Vulgare and Spontaneum barley, Dispersible clay, Rhizosphere, High energy moisture characteristic curve.