Abstract: Joint plane of rocks have a significant impacts on their physical and mechanical properties． The conventional triaxial compression test of natural phyllite was carried out to research the effect of the included angle between the maximum principal stress，joint plane，and confining pressure on the rock deformation-failure mode． The test results showed: 1) There were three deformation-failure modes with the included angle being in the range of 5 to 45: tension-shear composite failure，shear-slide composite failure across，and along the joint plane，and shear failure only along the joint plane． 2) The peak strength of the rock gradually decreased and the failure mode changed from the composite type to single type with increase of included angle． 3) The deformation and strength parameters of phyllite had obvious angle effect，especially on elastic modulus and cohesion． 4 ) The increase of confining pressure would weaken the mechanical effect of rock joint plane．