The characteristics of deformation failure and stress brittle drop of granite under loading and unloading conditions are studied respectively based on two unloading stress path cases and conventional triaxial compression experiments. The experiments show that the primary deformation of rock is rebound or tension in the (main) unloading direction

but plastic deformation in the non or subunloading direction is not significant. And the curves of stressstrain after peak strength present obvious brittle. Whilst the primary deformation of rock under loading is axial pressure deformation

and plastic deformation increases with the raise of confining pressure. The fracture is characterized by strong tensile

and all tensile cracks are fully developed. Furthermore

when the rock samples are unloaded in two directions

and even normal to unloading direction

subunloading annular tensile cracks are produced. The shear fractures is obvious comparatively when confining pressure becomes higher

and it develops following tensile cracks with more microtension cracks formed in two sides along shear plane. But the fracture is characterized by shear under conventional triaxial compression with little tensile cracks; the coefficients of brittles stress drop of granite is increased with the growth of confining pressure under conventional triaxial compression and reduced under unloading. When the initial confining pressure is the same

the coefficients of brittles stress drop under unloading is less than that under loading. In SchemeⅡ

the coefficients of brittles stress drop reaches negative when initial confining pressure is up to 30 MPa

and the one （R）is RⅢ>RⅠ>RⅡ in three test cases.