In order to study the influence factors of shear strength of granite residual soil in southern Jiangxi Province, X-ray powder diffraction and scanning electron microscopy were used to analysis the mineral composition and microstructure of biotite monzonitic granite residual soil and biotite granite residual soil in southern Jiangxi Province. Through triaxial consolidation undrained shear tests, the shear strength of undisturbed and remolded samples of two types of granite residual soils was also studied. The results show that the mineral compositions of granite residual soil in southern Jiangxi Province are mainly quartz minerals and clay minerals such as kaolinite and illite. The primary structural strength is obvious, and the shear strength of undisturbed sample is higher than that of remolded sample. The stress-strain relationship of undisturbed sample and remolded sample under various confining pressures is strain-hardening, which shows plastic failure; and the pore pressure-strain relationship is affected by large porosity and large coarse grains. Under low confining pressure, the relationship is first shear contraction and then shear dilatation, and always shear contraction under high confining pressure. The internal friction angle is obviously affected by the content of coarse particles, and the cohesion is obviously affected by the content of fine particles.