Abstract: To investigate the evolution of the microstructure of granite residual soil during triaxial shear,nuclear magnetic resonance(NMR)and scanning electron microscopy(SEM)techniques were employed to analyze the pore size and pore diameter distribution during shearing and to quantify the microstructural features. The results showed that the granite residual soil exhibited a three-peak pattern in the pore size distribution curves. The pores were classified into four types: micropores,small pores,medium pores,and large pores,with micropores and small pores being dominant. With increasing confining pressure and strain,the volume percentage of micropores and small pores increased,while that of medium pores and large pores decreased. Consequently,the overall porosity of the soil showed a decreasing trend. The microstructural parameters exhibited a nonlinear relationship with the shear stress ratio. The average shape coefficient,fractal dimension,and probability entropy changed rapidly in the early stage of shearing and stabilized in the later stage. When the shear stress ratio reached 0.77,the average shape coefficient attained its maximum of 0.408,the probability entropy reached a maximum of 0.994,and the fractal dimension reached a minimum of 1.25. The shear process of granite residual soil can be divided into three stages: early deformation,deformation reorganization,and shear stabilization. A close correlation exists between the changes in the microstructure of granite residual soil and its macroscopic strength characteristics.