In order to study the strength characteristics of granite weathering zone and the slope failure mode in south Jiangxi, the indoor rock mineral identification, X-ray powder diffraction and scanning electron microscopy were used to analysis mineral composition and microstructure of the granite and completely weathered. And through the uniaxial consolidation undrained shear test of completely weathered granite, the uniaxial and triaxial tests of moderately weathered granite, the strength and failure mode of weathered zone were studied. The results show that with the increase of confining pressure, the stress-strain relationship of completely weathered granite has transformed, which shows swelling and shear failure. The granite undergoes four failure stages under uniaxial test, the shear strength parameters of rocks are obtained by triaxial test, then the strength parameters of rock mass are obtained by Hooke Brown criterion inversion. With field investigation, there are five main failure modes of granite weathering slope in south Jiangxi, among which scouring failure accounts for a large proportion.