| This study presents results of an laboratory triaxial experimental program with respect to study the effect of wheat straw reinforcement on the shear strength of soil. Three axis shear tests were carried out under four reinforcement rates (0.1%, 0.2%, 0.3%, 0.4%) and three reinforced lengths (5, 10, 15 mm). The mesostructure changes of reinforced soil and plain soil during loading are compared and analyzed by using computed tomography(CT) scan image. The results show that: the shear strength and deformation resistance of wheat straw reinforced soil are significantly improved than plain soil, and the reinforcement effect is better when the wheat straw length is 10mm.In this condition, the cohesive forces of reinforced soil are 1.1 to 3.3 times that of unreinforced soil, the internal friction angle changes in the range of ±2 degrees. Compared with plain soil, the macroscopic shear failure of reinforced soil during shearing is not obvious, and all of them are bulging failure. When the confining pressure is small, the effect of reinforcement is significant, and the effect on the stiffness of soil is fine. With the increase of confining pressure, the effect becomes weaker. CT scanning results show that wheat straw reinforcement can restrict soil deformation and crack growth. It is concluded from this study that wheat straws are a suitable reinforced material for cohesive soil.