[Objective]Caragana korshinskii Kom. is one of the most widely used shrubs for slope protection and soil and water conservation in the northeastern Qinghai-Tibet Plateau and the Loess Plateau. The experimental study on the tensile mechanical properties of a single root of C. korshinskii was carried out to provide a theoretical basis for quantitative evaluation of soil fixation and slope protection of this plant. [Methods] Single root of C. korshinskii with root diameters of 2.33~9.16 mm at middle age was taken as the research object. The differences of tensile resistance characteristics of single root of C. korshinskii under different failure modes and different root diameter grades and their relationship with root diameter were compared and analyzed via single root tensile test, and the failure mode of single root and its stress-strain characteristics were further discussed. [Results] Two modes of failure of a single root, the periderm preferential breakage mode and the synchronous breakage mode, occurred when the roots were subjected to single root tensile test. The single root tensile force and single root tensile strength of the two failure modes were significantly different under the conditions of(2,4],(4,6],(6,8] mm and(6,8] mm root diameter grades, respectively (p<0.05). The difference degree of four single root tensile resistance characteristics indexes was different between different root diameter grades with the same failure mode. Under the periderm preferential breakage mode and the synchronous breakage mode, the single root tensile force of C. korshinskii increased with the increase of root diameter, there existed exponential and power relationship between single root tensile force and root diameter, respectively. In addition, the single root tensile strength, single root elastic modulus and single root limit extensile rate of C. korshinskii decreased with the increase of root diameter. The occurrence of these two failure modes of roots depends on the stress state of the periderm, thin wall tissue of middle column sheath, and the secondary vascular tissue when a single root is under tension. The stress-strain curves for the two failure modes can be divided into four stages: elastic deformation, elastic-plastic deformation, strain hardening and fracture failure. [Conclusion] It is necessary to consider the influence of root diameter and failure mode on single root tensile properties when single root tensile test is used to obtain single root tensile properties indexes of woody plant species. [ABSTRACT FROM AUTHOR]